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ERIN BURNETT OUTFRONT

"Significant Progress" In Boston Investigation; Interview with Congressman Michael McCaul of Texas, Chairman of the House Homeland Security Committee; Officials: Arrest Made in Ricin Letter Investigation; Sources: Possible Suspect Seen on Video

Aired April 17, 2013 - 19:00   ET

THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.


ERIN BURNETT, CNN ANCHOR: Thank you very much to you, Wolf. OUTFRONT next, we begin with breaking news, a significant development in the investigation here in Boston, according to sources, police are looking for someone they saw on video as a possible suspect.

Plus what we're just learning about the devices used during the bombings and how authorities are using that information they were trying to piece together to locate the attacker.

And another letter containing the poison ricin sent to one of our lawmakers in this country, this time it was to the president of the United States. Special edition of OUTFRONT live from Boston tonight. Let's go OUTFRONT.

Good evening, everyone. I'm Erin Burnett in Boston. And we begin OUTFRONT tonight with breaking news, a possible suspect in the Boston bombings. Here's what we know at this moment.

According to sources who talked to CNN, authorities have identified a possible suspect based upon analysis of video of a department store, Lord & Taylor Department Store right near the second blast.

Now no arrests at this point have been made, but federal investigators say that they have made in their words, quote/unquote, "significant progress in the case." Sources tell CNN that the possible suspect is being described as a male who was wearing a white baseball cap backwards, a light colored hoodie and a black jacket.

We're awaiting an FBI press conference within the hour and we're going to bring that to you live as soon as it happens. Obviously some question as to when that will happen, if that will happen.

I want to first bring in our chief national correspondent John King. He is from Boston, has been working his sources on this all the way through. What is the latest that you know on this possible suspect?

JOHN KING, CNN CHIEF NATIONAL CORRESPONDENT: The latest is that video analysis overnight, Erin, led authorities to believe that they had a breakthrough and that video analysis was from a department store, just a couple of steps from here, Lord & Taylor, which is very close to the second explosion site.

The video reviewed from that site I'm told by several sources now shows what is they believe to be the drop, the placement of the second explosive device. There was that enhancement of that video where authorities believe they have a pretty good representation, pretty good facial on that one suspect.

Now my understanding is that the images of that have been distributed to law enforcement officials, there was some confusion earlier in the day, but now we're getting it from the FBI, from here in Boston, from the Justice Department in Washington, from the Boston police and the governor of Massachusetts told Wolf Blitzer a short while ago, no arrests, no one in custody.

There were questions earlier as to whether there's a semantic debate here. I will say though that I spoke earlier today to the Boston Mayor Thomas Menino and he said that when he was briefed this morning he became quite optimistic a big breakthrough was imminent.

(BEGIN VIDEO CLIP)

MAYOR THOMAS MENINO, BOSTON: The government on Monday afternoon a lot the investigation that's going on. I was briefed early this morning about the investigation and I think we're making head way. I hope that in the near future we have a definitive answer to this question of who did it. But until the FBI is satisfied they have the right person, we can't go public on it at all.

(END VIDEO CLIP)

KING: Yes, the mayor also confirmed source accounts that it was Lord & Taylor, was the department store where they got the best video. I was also told by a source that there was a video by a Boston television station that was around that spot at the same time was also helpful in the investigation there.

And we know they have been going through this definitely much more optimistic today that from the video and now they have what they believe is the placement of the second device that gives them a much better time frame. They're going back and looking at the first location as well, trying to sort things out.

A lot of optimism tonight, but the fact that this public briefing by the FBI and other authorities, was supposed to be at 1:00, it's moved to 5:00 then it was delayed again, and now we're hearing it may or may not happen at all today.

But that raises some questions. The public reason they are saying is because that courthouse was briefly evacuated because of a bomb threat, but curious why we got zero public information from the authorities.

BURNETT: I mean, you know, who knows? And obviously viewers are wondering and they're speculating and asking questions as are we. But what is the whole question today of in custody arrested, what does that mean? Do they really know where this person is, and as you have emphasized, the video that they have from the Lord & Taylor is the placement of the second explosive device so are there still questions about whether it was one person or multiple people and who would have dropped the first one?

KING: There is other information tonight we're trying to confirm about the possibility of a second suspect, I'll leave at that for now. But we do know in this first one here, I was told by several sources they have a very good facial based on the video enhancement of the Lord & Taylor video at the second explosion site.

Now as for the custody, look, we have both from a federal official, a Boston official saying that an arrest had been made or at least an operation to arrest someone was under way. There is no question those officials and other several other media organizations reported the same thing.

There's no question now that officials were out ahead of themselves because now we are told publicly by the FBI, by the Boston Police Department, by the governor of the Massachusetts that no arrests have been made.

The governor was quite adamant. He said this is not about semantics. He said based on his knowledge, no arrest, no one in custody and no one being questioned. Obviously, you can bring someone in to question them and they are not arrested.

But the governor's understanding was that none of those stays. He says that base it upon his best information there was nobody talking to law enforcement in any capacity.

BURNETT: Well, a lot of it would seem at this point that at least they would have the strong desire to the next time they speak have more -- you know, have something definitive.

I want to bring in a former FBI profiler, John Douglas along with Mike Sullivan, a former attorney in the district of Massachusetts and former acting director of the ATF into the conversation here with John and myself.

Mike, let me ask you what do you make of what John's reporting on here? That there is possible second suspect, we don't know at this point. Obviously one suspect that they have on the video, but related to the second explosive. When you put all that together, what do you take away?

OK, he can't hear me. Let me go to you, John Douglas, former FBI profiler. When you listened to what John was saying, right now, there's a fast and furious scramble tonight whether to find this person or arrest this person, perhaps another suspect. Who do you think this person is?

JOHN DOUGLAS, FORMER FBI PROFILER: Well, that's a really the most difficult part in this type of case, it's not like a case such as the Una-bomber profile in the early '80s. It's extremely difficult because what you're trying to determine is the motive. It's not like going to a homicide and you're trying to do victimology on a specific victim, you analyze the forensic evidence, the autopsy report. Here the victims are so random you really then have to shift more to the forensics.

So when I work a bombing case, I would go to our lab, tell me the degree of sophistication or the lack of sophistication of this bomb. Is it even dangerous for this person that's making this device or is it something you can pick up off the internet and do it yourself?

And then based upon that how things have changed. You really have to rely on information from the public. The downfall of the Una- bomber Ted Kaczynski was when the manifesto was written. Then we had something to analyze.

In this case we have no one claiming responsibility. We have not received any communique as far as we know. And again, unfortunately, many times, in our work we have to wait for multiple cases to try and tie in, if there are other cases that will happen in the future. So it's really, really a difficult case.

BURNETT; And what does that lead you to believe in terms of people have wondered, that kind of, quote/unquote "lone wolf" nature of this type of person. You know, you have law enforcement officials say look, somebody knows this person.

Somebody is this person's wife, this person's sister, this person's daughter, this person's friend, this person's co-worker. Has anyone done anything unusual you might know this person? When law enforcement is reaching out in that manner, do you think it indicates this person truly could have been operating alone?

DOUGLAS: Well, particularly it's a good technique used by law enforcement because what you're trying to do is you're -- when you can't put a profile together. You're trying to identify behavior. And generally, offenders like this do not work in a vacuum.

There's something, they'll speak about their problems, whatever their issues are, whatever their motivations are, they also will oftentimes try out the device, they just don't show up and for the first time and use this device. They'll use smaller devices just to see if in fact will work.

And kind of go through an exercise, kind of go through a practice, but the police are doing the right thing, but I believe that the solution of the case is going to come from the public. Unfortunately, again in law enforcement, we have to wait for the offenders to make a mistake.

The mistake that this offender would have made is that he wasn't aware of all the surveillance cameras that were on at that particular time, people with their phones capturing the runners as they crossed the finish line so we're going to have to rely on the public.

BURNETT: John, thank you very much for taking the time and of course, to our John King for his reporting on the very latest that we know. And as we said a question mark right now as to whether there will be a press conference from law enforcement authorities at some point in this hour. But we are monitoring that and we will bring it to you live if it happens, any updates we have as we get them.

Still to come, we're going to go through the clues of what actually was in those bombs, analyzing the nails and the BBs in the bombs that could actually lead police to the terrorists. We're going to go through that bit by bit.

And something strange happening in cyberspace, investigators are monitoring chatter on Jihadist web sites and finding something tonight surprising. Talking to our sources right now and as soon as we have that we're going to bring it to you.

(COMMERCIAL BREAK)

BURNETT: Tonight investigators are scouring every clue from the mangled remains of the pressure cooker, the nails and the BBs that were used in the bomb to try to find out exactly where the parts were purchased and who bought them.

As we have shown you there are pictures that show perhaps part of a serial number that might give you at least an indication as to the location of the manufacturer if not the point of final sale.

The evidence could provide a major break in the case. Our Tom Foreman is OUTFRONT. Tom, as you have been looking through this, how are investigators trying to look through the origin of the bomb parts?

Because I know some of the pictures, which we'll show again to our viewer show parts of serial numbers but not in full. It's tantalizing, but not all the information.

TOM FOREMAN, CNN CORRESPONDENT: Well, one of the keys to the way they're going to track this down, Erin, and you mentioned just a minute ago, pictures. We said yesterday that pictures are going to be key to all of this and today, they have been very excited about this particular picture, which was taken not far from where you're standing right now, Erin.

This is a picture by a TV station that shows a package of some sort in front of a railing that has people gathered behind it. Coupled with another image that has them very excited today, video coming from a camera on top of a Lord & Taylor's across the street.

Let me jump from around behind that camera and show you the point of view if you were up there looking down. See where that's pointing at. See that mailbox down there, the truck on that area? That's where the bombing took place.

Let's get our model and talk about the placement of everything here. You right now are right over in this area. This has been CNN's position all day over here. Lord & Taylor's is right over here, not far away. It's yellow in our model, if I can bring it up right now. And look very closely here, because this camera that we're talking about is actually right up there on the corner of the building and that is the second explosion site right down there. You can see that is a completely clear line of sight. If in fact they have an image of a bomber, it would be a good one from that angle. Then you could see the other side up the Fifth Street. That was the first explosion, that was the second explosion.

Why does all this matter? It matters, Erin, because as you try to get to that physical evidence, it really helps if you have some idea whom you're following. Even if it's six or seven different people that have been identified in these shots, you can start tracing them and trying to find the real origin of these relatively common items that were used in the bomb. Erin?

BURNETT: Common items. We talked about a pressure cooker and look, we're looking at one today. It is - it is a domestic item. But Tom, they're also trying to -- in addition to going through the video surveillance, they're trying to essentially rebuild the bombs right?

FOREMAN: Yes, exactly. That's exactly what they're doing, Erin. Look at the items you mentioned a minute ago. The backpack that was involved here. This is a common item you can find anywhere, of course. Sure you got the pressure cooker, this is one of the items. We talked yesterday about how in the explosions, parts of this may have actually been blown up in the air. In fact, the lid was found on the roof of one of these buildings out here. And then there are other things like ignition pieces.

Why do they want to put all this together? Because the configuration of all these things together, Erin, will tell you whether or not you have all the parts. Because the part you're missing may be the key part that links somebody who you spotted on this street with all of this stuff. If you can link those together, you not only have a better chance of narrowing in on who was here and purchased this stuff and making an arrest, but also having a case that can stand up later on when you have to deal with all of that. Erin?

BURNETT: All right. Tom Foreman, thank you very much. I want to bring Mike Sullivan OUTFRONT now. Former attorney in the district of Massachusetts. And the former acting director of the Bureau of Alcohol, Tobacco and Firearms. Good to see you, sir. Appreciate it.

So, we hear Tom reporting on the importance of rebuilding these bombs. Why is that so significant, and what information are they going to be able to get from that ideally?

MIKE SULLIVAN, FORMER U.S. ATTORNEY: Well, several. First, it's going to be very case specific in terms of this particular investigation. It may help in terms of the timeline as well. How the bomb itself was detonated. Was it done remotely, was it done by way of a timer? That could be important if you look at the timeline of the events.

And then certainly the evidence here. Where was it sourced from could help in terms of building a case. So, there are several things going on. You also want to make the strongest possible case. You want to see if there's some evidence here that can identify the suspect as well. And if there's any particular signature of the bomb, there might be signatures of other bombs that they've been that might identify the bombmaker or bombmakers.

BURNETT: And when they look at the pieces that they've been able to identify from inside, we have been showing our picture to our viewers if you see these wires on the ground right between these cones. W also sent a picture of some of what appears to be melted matter, whether it BBs and nails. But what does the substance of the device tell you?

SULLIVAN: In terms of things like the beebes and the nails, that obviously suggests that they're trying to get maximum injury and maximum death as a result. And that's the shrapnel. Where they place it also determines that they may get some additional shrapnel as well if they're doing it, say, near a mailbox, a metal mailbox or a can as well. They use that to cause maximum injury.

BURNETT: And let me just ask you right here. So I just want to hold this up. This is obviously where everything was stored and it was one of these, I'll hold it up. It's a pressure cooker, basic domestic item. Does this make it stronger or weaker?

SULLIVAN: Well, this actually becomes shrapnel as well. So what you want to do is compact something inside here. Then you have to activate the bomb. You have to detonate it, and that's where you get the wires and the circuit board in order to be able to communicate. And get a spark. A spark essentially would ignite where you're using it here, whether it's military-grade. They say it's likely not military grade in terms of the compound. So, and that pressure will build up and obviously explode.

BURNETT: And your understanding from what you have seen so far, and I know you have been going through the pictures and the video, that this would have been a remote detonation?

SULLIVAN: Well, I'm going to let the experts make that determination and they will. All the material that they have is now at Quantico. The experts essentially that do this type of post-blast investigation will come to some conclusion as to whether this was detonated remotely or detonated by some way via timer.

BURNETT: A time. All right, well thank you very much, Mike. We appreciate it.

And as we told you last night, 24 hours ago in fact, the chairman of the Homeland Security committee was saying he was hoping some of those forensic would be back from Quantico within 24 hours. The chairman of the Homeland Security committee will be back with us later on this hour. And we're going to see if we have some news from that. If we have some more information about the bombs themselves.

Also still to come, authorities are doing everything they can to try and locate the bomber. What the chatter on jihadist Web sites reveals about who might be responsible. They have been combing through this. And we have new details for you next.

Plus immediately after the blasts, EMTs sprung into action. They risked their lives to try and save others. We're going to meet the man who treated all of the three victims who were killed in the bombing.

(COMMERCIAL BREAK)

BURNETT: All right. We begin with breaking news here. Deborah Feyerick is with me and she has some new information on what investigators are looking at. Some photos.

DEBORAH FEYERICK, CNN CORRESPONDENT: Yes. They're looking at a lot of photos. And what you have to understand is that this is like a big montage. And what they're doing is they're taking surveillance photos. They're piecing everything together bit by bit. One photo that was making the rounds pretty early on in the day that's of particular interest is of two gentlemen who were seen by the finish line. They're talking with one another and they're each carrying bags that are a little bit out of proportion. Those are the kinds of things that investigators are looking at.

Nobody is calling them anything more than witnesses who they would like to speak to. And that's one of the things -- there are other groups of men they're looking at as well. People who are carrying things that maybe they shouldn't have been carrying that close to the finish line. But these two are of particular interest. They're trying to track them down. And again, it did reach the higher levels today, people looking at this photo.

BURNETT: Right. And I know you're saying at this point, they just want to talk to them and find out what they knew. But to make it clear, two men near the finish line that had bags that were really stuffed.

FEYERICK: And the things that we've been getting from the FBI, for example one was the backpack, another may be sort of a duffel or a rucksack. So, those descriptions are consistent with one or more of the pictures of people in the crowd that they're looking at. So, again, they're really trying to get rid of all that sort of visual debris and focus in on those folks who are of most import who they think may have had something to do with this.

But again, you take a big picture, you got to piece it together and then you got to isolate those most important elements.

BURNETT: Right, try to find those people. In this case, you're saying it was two men. And the question is now, how many people were involved, and you got to go through every one of them. Now, (INAUDIBLE) we have been looking at the question of foreign versus domestic terrorism, which still remains the huge question out there. And the chatter they have been monitoring on quote unquote "jihadist Web sites." What have they found?

FEYERICK: This is what's so fascinating. I spoke to a number of terror experts today. One of them in the United States, another internationally, to get his take on what they're thinking about over there. What's so interesting is that there has been very little chatter, almost no chatter. Usually these Islamist jihadi forums that light up whenever there's been some sort of attack, they in fact have been quiet. Nobody has claimed credit for this. Nobody related has claimed credit for this as we have seen, for example, in other bombings.

Also what's -- understand usual, according to the person I spoke to overseas, he said, this one is strange, this one feels different. The others had a certain pattern. This one doesn't have that pattern. And also the device. The device that was used -- when you think of all the attacks that have been tried on the United States, the Times Square bombers, others. What's unique about this device is that it actually worked. So even though the device itself is not sophisticated, it was able to do what it was supposed to do. Others, for example the Times Square bomber, didn't do it. So, there was a level of sophistication to these two devices. And that's another thing that actually doesn't fit the pattern of a transnational attack.

BURNETT: All right, well, Deb Feyerick, thank you very much. She's going to continue to talk to her sources. But again, the intelligence she's just gotten is that there's some photos that law enforcement officials are focused on, including one which is two men near the finish line with bags that appear to be stuffed more than they ordinarily would have been.

Still, to come, more of our breaking news coverage of the Boston bombing. We are going to be joined by the chairman of the House Homeland Security Committee. Chairman McCaul is going to join us with the very latest on the attack. What he knows, what he knows about the suspect and what he knows about the bomb.

And a letter sent to President Obama has tested positive for the powerful poison ricin. What those two letters mean for an America on edge tonight.

(COMMERCIAL BREAK)

BURNETT: Significant progress has been made in the Boston bombing investigation. That is the latest information that we have from the FBI. We now know authorities have found new clues in Lord & Taylor surveillance video, which is right near where I'm standing right now.

The camera was positioned just across the street from the second location and as you can see, there was quite a lot of space there, they had a completely clear view as our Tom Foreman has reported, that camera did, of the location for second exploded device.

They're now looking for a man who was wearing a white baseball cap, a light colored hooded sweatshirt and a black jacket. Now, we do not know if investigators have yet been able to identify this man. But we just reported a few moments ago that they are now looking at other photos, including one of two men by the finish line, both of whom had bags who seemed to be stuffed over capacity.

I want to bring in Drew Griffin now.

And, Drew, what is the latest on what investigators know. We have been waiting and waiting for this FBI press conference and I believe you have some more detail on what's going to happen. DREW GRIFFIN, CNN CORRESPONDENT: Well, yes, 1:00, 5:00, and then a delay of a couple of hours and then another delay, then a tweet that said 8:00 and now I'm just reading a tweet from Boston Police Department, the FBI has cancelled the 8:00 p.m. briefing tonight. There will be no briefing. So they may be making significant progress but they're not going to share that officially with us, leading us to rely on our sources, some speculation and just wondering what this actually means in terms of this investigation.

But that's about all I can tell you from here. A lot of journalists as you can see behind me have been waiting all day for this to try to get some kind of official statement on any of all the information that's been disseminated through sources, but we're not going to get that tonight now, Erin and, you know, I'll have to leave it up to your guests to speculate on what exactly that means -- Erin.

BURNETT: I mean, that is -- that is a question mark, I know, Drew, some have said, well does that mean that they're -- they have information that they're not yet ready to share, does it mean they haven't yet tied together strings they want to tie together? But those are the question marks out there.

I want to bring in Congressman Mike McCaul. He's the chairman of the House Homeland Security Committee and get answers to the questions Drew just posed right away.

Chairman, do you know why this press conference has been delayed and delayed and delayed?

REP. MICHAEL MCCAUL (R), TEXAS: You know, I don't. And as I have been saying for a long time, this surveillance video now we know from Lord & Taylor, and private videos, it's going to be one of the keys to this case. In addition to the forensics on the bomb itself, which is being evaluated at Quantico as we speak. And we hope that those results will come out shortly.

But as for the delay of the press conference, I don't know. I did come out earlier when there were reports of a suspect in custody confirming that that was not true.

BURNETT: Confirming that was not true. And what is it that your latest understanding on that as you and I have spoken over the past few days you said, look, the first 48 hours are the most crucial. And here we are now. But do you feel that they have made, as they say, significant progress?

MCCAUL: You know, I think they have. The first 24 hours in a murder case is key. You don't want the trail to get too cold and too scale.

On the other hand, they're going to have the best evidence right now in my judgment. Are these videos that were taken from security cameras outside Lord and Taylor, that the FBI is poring through, my guess is they have possible suspects they have seen on this videotape that they're looking at and at some point in time will come back to the public to help their cooperation to track them down. That, coupled with the device itself and the forensics, the FBI, what the FBI does best is its forensics of bombing devices. They're very, very good at tracers, fingerprints, footprints on these devices to find out where it was purchased and who purchased the materials. So, from there, they would execute search warrants and hopefully find the terrorists.

BURNETT: And, Chairman, let me just interrupt here, we do have some breaking news.

There has been an arrest, sir, you probably are aware of, in Mississippi. There's been an arrest in the ricin case according to two federal law enforcement officials here at CNN. The arrest happened in the Tupelo, Mississippi, area. Of course, one of those letters, as we all know, was sent to Senator Wicker of Mississippi.

Can you tell us any more about this?

MCCAUL: Yes, I knew they had a suspect in this case, and I'm glad to see they have been able to apprehend and arrest this individual. And I would again make the assertion that it really has no relation to the Boston bombings, it's very reminisce end of the anthrax attacks after 9/11 on Capitol Hill. As it may, it's very dangerous when you have someone sending, you know, ricin to senator offices.

You know, the state of security on Capitol Hill is at all time high right now to protect members of Congress. We're very concerned about these packages. The good thing is, after 9/11, we implemented a procedure where they go through an outside mail facility. So, once they're detected there, they get nowhere close to the members of Congress, and that's a good thing.

BURNETT: Let me ask you another question about the situation in Boston. Just in terms of whether the suspects, the people that they talking, looking at right now in some of those photos, can you tell me whether they're confident, whether you're confident from your briefings that that person or those people are still in the area, are still nearby, or do they think they could have fled the country or gone far away?

MCCAUL: You know, I honestly can't answer that question. I think that's one of the biggest issues with this case, is that when every stay passes -- you know, remember the Saudi suspect kind of washed out?

So the perpetrators are still out there, and every day that passes, the case becomes a little bit colder and more difficult to piece together. But I'll remind your viewers, though, the '93 World Trade Center bombing case was masterfully put together by the FBI and the U.S. attorney's office where they pieced together this forensics from the bombing device at the World Trade Center and were able to attribute that back to the terrorists, that being Ramzi Yousef and the blind sheikh that perpetrated that.

So, I'm hopeful that will happen in this case. I do think there's general sense of more optimism, though, within the FBI and the Justice Department, and the Joint Terrorism Task Force in Boston that they're getting closer.

BURNETT: All right. Well, sir, thank you very much, good to talk to you again tonight and we appreciate you taking your time, and all the latest.

And, again, the breaking news that we have is that we can confirm that there was an arrest in the ricin letters that were sent to Capitol Hill. The arrest was a man in Tupelo, Mississippi, which is the hometown of Senator Wicker. Of course, the senator from Mississippi who received the first of those letters, one to preliminary test did test positive today. That went to the president of the United States as well.

Rescuer workers at the scene of Monday's bombings went into overdrive. Within 18 minutes of the blast, EMTs say that they had cleared the votes of all critical care victims. They risked their own lives to try to save others. It's in those moments that you're supposed to run away that they run to the scene of the destruction.

As Poppy Harlow reports exclusively tonight, those heroes are now grappling with the horror of what they saw.

(BEGIN VIDEOTAPE)

POPPY HARLOW (voice-over): Even 32 years as an EMT can't prepare someone for horror like this.

(on camera): How hard was Monday?

MIKE BOSSEE, BOSTON EMT DEPUTY: It was the city's worst day in our department's history.

HARLOW (voice-over): Mike Bossee has been saving lives since he was 22 years old. On Monday, he was the finish line command in charge of EMT response to the terror attack.

He saw the worst of it.

BOSSEE: I saw all three fatalities including the 8-year-old.

HARLOW (on camera): You saw Martin?

BOSSEE: Yes. Plus, the kids that were hurt, the kids that look like my kids when they were growing up.

HARLOW (voice-over): Kimberly, Robert and Christopher were right alongside him.

ROBERT STEARNS, BOSTON EMT: We were down at Boylston and Berkeley about a half block up when we first heard the first explosion.

KIMBERLY HORNE, BOSTON EMT: Our first patient was a 17-year-old female. She had blast injuries and shrapnel wounds and an arterial bleed.

HARLOW: The same age as her son.

And then they treated a 44-year-old woman, even as reports of more potential bombs were coming in.

STEARNS: She had pieces of the fence sticking out of her legs and she was burned up a bit and as we were working on her like Mike was saying is that police tapped her on the shoulder and said you need to go, there's a package behind you, you got to go now and said we can't go now, (INAUDIBLE) we need to go, I'm like we can't leave her behind.

HARLOW: Unwilling to leave, no matter the danger -- heroism that prevailed above evil.

CHRISTOPHER HOLGATE, BOSTON EMT: I was right there, right next to, very close to where the explosion was. And there was a whole bunch of patients on the sidewalk and everyone was -- wow --

DR. PETER BURKE, BOSTON MEDICAL CENTER: I cannot sing the praises higher for the EMS Services. They were there. They triaged patients. They brought them to several different hospitals across the city. It allowed the hospitals to step up and take care of those patients.

HARLOW (on camera): What was the best that you saw that day?

STEARNS: I think everyone helping, not just how fast all of our people came and helped. Just the general public, strangers helping other strangers that didn't know them, people that had no training just wanted to help do something.

HORNE: I couldn't believe how many people were still there.

HARLOW: To help.

HORNE: Yes.

HOLGATE: Everyone just ran in there to help.

HORNE: People look for heroes, but in Boston, you just have to look next to you.

HARLOW (voice-over): On a day marred by the worst of human kind, we saw the best of humanity.

BOSSEE: If I could, I would give them all medal, because they all deserve.

(END VIDEOTAPE)

BURNETT: Poppy, I know when you see it's so humbling to see them. I know they have been trying to get updates on the people they saved, have they been able to do that? HARLOW: They have. Some of them have, not all of them. But, you know, they see their victim at the worst state and they hope they live and they make it through and they are full recover.

One of the EMTs told me today that they were able to go to Boston Medical Center today to see their patients one of the patients had improved from critical to serious. And many would think serious isn't good, but serious is better than critical, and that is what they wanted to see is improvement.

One of the things we also talked about was coping. How did they cope? I mean, this is -- you know, what about the trauma that they have gone through having to treat this? It really was like a war zone. I mean, the IE type explosives that exploded.

They said they have each other. Each other, they can understand. Maybe their friends and family can't understand what they've gone through, but their fellow EMT workers can.

And they are amazing, and I applaud them and we all applaud them for running when so many people's instincts would have to run away. You wonder what would I have done? They didn't hesitate.

BURNETT: They went in and saved the lives. And how amazing it is they want to go and meet with those people and follow up with those people that they care.

HARLOW: Yes. And I said do you still want to keep doing this? Are you sure? Because none of them have experienced something like this and they said no question, absolutely.

BURNETT: Wow. Poppy Harlow, thank you very much.

You see some of the heroes from this horrific attack.

Still to come, we have more of the breaking news on the arrest of someone who allegedly sent letters with ricin to the president of the United States and a U.S. senator. We got breaking news after this.

(COMMERCIAL BREAK)

BURNETT: All right. I'm back here with Anderson Cooper. He's got a look at what's coming up on "A.C. 360."

ANDERSON COOPER, CNN ANCHOR: Yes. We're going to be talking to Governor Deval Patrick, who's going to be joining us here.

I'll also talk to first responders and firefighters who were at the finish line. They have been there for years. It's kind of a tradition in their firehouse. And they feel very thankful that they were. They sprang into action and saved lives. They're going to talk about what they saw and how they figured out who to treat first and what this experience has been like for them.

BURNETT: It's incredible for those people who have no idea this coming. COOPER: Yes. And yet -- I mean, we've seen again. It's been repeated so many times, but it bears repeating because there's so many heroes who ran toward the explosions, citizens, first responders, firefighters, police. And so, we're trying to highlight as many of them as possible.

BURNETT: Yes, more heroes.

All right. Well, Anderson, we'll be on with us just for a few moments.

COOPER: Yes.

BURNETT: We'll see you then.

We have some breaking news, though, now that we want to share with you on the ricin investigation. We are just learning that an arrest has been made in the investigation of two letters that have been -- one was intended for President Obama, the other for Senator Roger Wicker. They tested positive for the deadly poison ricin.

Our chief congressional correspondent Dana Bash is OUTFRONT with the latest.

And, Dana, what are you learning? An arrest of a man from Mississippi, right?

DANA BASH, CNN CHIEF CONGRESSIONAL CORRESPONDENT: That's exactly right. And we now have this from multiple law enforcement officials. I was just texting with one that just confirmed the news as well here.

And the news is that this man was arrested in Tupelo, Mississippi, and the reason why this is interesting is because that happens to be the hometown or at least the area where Senator Roger Wicker is actually from. Now, he, of course, was one of the intended recipients of the letter. The other was President Obama which we learned earlier today.

We don't have much information about this man except that he was arrested.

The thing I can tell you is that late yesterday when senators here in the Capitol were briefed, one came out and said, Senator Claire McCaskill, and told reports, that the initial suspicion was it was a specific man back in Mississippi who had been, for lack of a better way to say it, harassing Senator Wicker. So, they had a pretty good sense of where to find this person, and it's clear really within 24 hours they went and they found him.

BURNETT: And, Dana, I know there were some other scares today. But from your understanding of this arrest, of this man from Tupelo, Mississippi, hometown of Senator Wicker's, this is the only person who is responsible for all of the letters, right?

BASH: They believe so. They believe so. And I'm sorry, Erin, literally as you were asking me that question, I just looked down at my phone here and got another text from my source who said this was an FBI grab based on United States Capitol Police information.

So that's just a little bit more -- a nugget of how this went down. Of course, hopefully we'll get more as this unfolds. But they believe that this was the one man who sent the letters. But you're right. There was a lot of drama here on Capitol Hill, because there was so much anxiety. There is supposed to be no mail delivered, at least until Monday.

However, there was somebody walking around this building where I am, the Russell Building and also the Senate Hart Office Building, handing to the front offices some sealed envelopes, which produced a big scare. The hallway down here was locked off. There was partial lockdown in the Senate Hart Office Building for a couple hours.

Everything was all clear at the end, but it really does go to show you how anxious people here are. Particularly since this was the place not long after 9/11 where anthrax was sent and really did disrupt things and people, including myself, were on Cipro and other antibiotics because of the scare.

Now, ricin is a different kind of issue than anthrax. But still, certainly is an eerie reminder of how you have one big thing like we have in Boston and then something else happens and it makes people very much on edge, as you can imagine.

BURNETT: It does, and an entire country on edge. Thank you very much, Dana, with the very latest on that, I'm understanding there was just one person responsible, that person now arrested from the hometown of Senator Wicker's, Tupelo, Mississippi, arrested for sending those ricin-laden letters.

I want to bring in our chief medical correspondent, Dr. Sanjay Gupta, along with retired Colonel Randall Larsen, who's a bioterror expert.

And let's talk a little bit more about this.

Sanjay, I mean, obviously, what Dana was talking about and capturing it so eloquently was just the fear that this creates. And obviously not linked to this event, this understanding is they weren't certainly talking -- did he choose this time to do it because of this, who knows?

DR. SANJAY GUPTA, CNN CHIEF MEDICAL CORRESPONDENT: Right.

BURNETT: But ricin itself, how hard is it to get ahold of and how dangerous is it?

GUPTA: You know, there's sort of three things you want to think about. How hard it is to get ahold of, how easy it is to weaponize --

BURNETT: Right.

GUPTA: -- and then disseminate.

You know, it's castor bean oil. So you can get castor beans for sure.

But that second step, Erin, to turn into a weapon of some sort is hard. You've got to make it into these very small particles that potentially could be inhaled into the lungs.

So I think in general, turning it into a weapon is a tough thing to do. It's scary, as you point out, anxiety-provoking. And if it did turn into a weapon, it could be very deadly. But I think that that's hopefully not what we're talking about here.

BURNETT: Right.

And, Colonel Larsen, I know when we're talking about the form it could take, obviously, is very significant. The form in the letters was not the most potent form, but still, this person who lives in Tupelo, Mississippi, was able to get it this far along. Is that something that concerns you?

COL. RANDALL LARSEN, USAF (RET), CENTER FOR BIOSECURITY AT UPMC: Well, from a legal perspective, Erin, this is a very serious crime and if convicted, it will be a very severe punishment.

From a national security, perspective, though, mailing ricin -- home-brewed ricin -- to someone is not a threat to a large number of people. For instance, a half a pound of dry powdered anthrax, that could kill tens of thousands of people. But an envelope with a little ricin in it, which probably not properly made is -- I would say a .38 caliber weapon is probably a greater danger.

Nevertheless, this is going to be a very serious crime, and hopefully we've got the perpetrator in custody.

BURNETT: And, Sanjay, on that question, when he talks about ricin versus anthrax, remember those awful anthrax scares that Dana was talking about, which is more difficult to obtain?

GUPTA: It's a good question. I think probably as colonel was saying, the anthrax, that's a bacteria, that makes those spores that reintroduces. Ricin is just a protein from a plant. So, in some ways, that's probably easier obtain. It also takes less anthrax to kill an individual versus the ricin. They both require very, very small amounts but I think in terms of obtaining, it's probably the anthrax, something that can occur naturally, but difficult to isolate.

BURNETT: Colonel Larsen, what would be your biggest fear when you think about someone sending something through the mail?

LARSEN: Anthrax is one of the easier ones to make, easier ones to isolate, as Sanjay said. And that's one that we're concerned about. That one -- that's not contagious. Small pox, which is contagious and deadly, those are the two greatest threats, and thankfully, that's the two pathogens we're most prepared to respond to that we have worked on very hard since 9/11 and the am Amerithrax case.

BURNETT: But this country has worked on it, Sanjay. But -- GUPTA: It is a big but, because, you know, these things, we don't talk about these things enough, unless something like this happens. And I think if you start talking with people at the CDC who say, look -- and Colonel Larsen for that matter, you know, how prepared are we, how much have we done to be able to protect not only communities but the country as a whole. I think it's tough to say.

You know, you talk about small pox, that's always sort of the worst-case scenario. But this will be -- I think serve as a reminder, I think.

BURNETT: All right. Colonel Larsen, Sanjay, thanks very much to both of you. We're glad to be able to report there is an arrest in that awful ricin case tonight.

We're going to be right back.

(COMMERCIAL BREAK)

BURNETT: All right. Our two breaking headlines of the hour. There has been an arrest in the letters that were laden with ricin that were sent to a U.S. senator and to the U.S. president. A man who lives in Tupelo, Mississippi, the hometown of Senator Wicker, the first recipient, of course, of one of those letters. So we have an arrest there.

And the other news that we have, investigators focusing in very closely on one specific photo that has two men with bags that seemed to be more full than they should be near the finish line. They're looking at a lot of photos. They say they just want to talk to these people.

But that is the very latest that we have. They're looking at pictures of congregated groups of men to try to ask those questions.

We'll be back here live at 11:00.

In the meantime, though, "A.C. 360" starts right now.