The terror at Michigan’s Oxford High School that left four dead started with gunfire, yelling and an urgent message on a loudspeaker. Then frightened students barricaded doors, phoned for help and picked up anything they could grab in case they needed to fight back. Aiden Page, a senior, was in a classroom when he heard two gunshots Tuesday afternoon – part of what authorities called a sophomore’s “absolutely cold-hearted, murderous” rampage that left four students dead and seven other people injured in the deadliest shooting at a US K-12 school since 2018. Just like in the active shooter drills they’d practiced, Page watched his teacher run in and lock the door, then students shoved desks against it, he told CNN’s Anderson Cooper. “We grabbed calculators, we grabbed scissors just in case the shooter got in and we had to attack them,” he said, describing how a bullet pierced one of the desks they’d used to block the door. In a sign language class, freshman Mark Kluska heard someone announce a lockdodwn over the school’s loudspeakers. His teacher shut the door and fixed it with a metal doorstop. “I started realizing it was real when I began to hear yelling,” Kluska told CNN. Later, someone outside the room who claimed to be with the sheriff’s office told Kluska and his classmates that all was safe and they could come out, a video the freshman recorded shows. “We’re not willing to take that risk right now,” the teacher replies. It’s not clear who the person at the door was. But the teacher quickly signaled students to scramble out a first-floor window into the snow, Kluska said. From there, they raced across a courtyard to another part of the building, where a law enforcement officer herded them to safety. Oakland County Sheriff Michael Bouchard confirmed during a news conference Wednesday the suspect never knocked on any doors. More than 100 calls to 911 were made. About two to three minutes after officers arrived, they found a 15-year-old suspect, later identified as Ethan Crumbley, and took him into custody without incident, Bouchard said. Crumbley has been charged as an adult with terrorism causing death and four counts of first-degree murder. He also was charged with seven counts of assault with intent to murder and 12 counts of possession of a firearm during the commission of a felony, Oakland County Prosecutor Karen D. McDonald said. The suspect’s lawyer entered a plea of not guilty on his client’s behalf at Wednesday’s arraignment. The judge scheduled a probable cause hearing for December 13 and a preliminary examination hearing for December 20. During Crumbley’s arraignment Wednesday, Lt. Tim Willis said two separate videos were recovered from the suspected shooter’s cellphone in which he talked about shooting and killing students the next day at Oxford High School. In addition to the cellphone, a journal was recovered from Crumbley’s backpack detailing his “desire to shoot up the school,” Willis said. One of the dead was 14 years old The four students who died have been identified as Madisyn Baldwin, 17; Tate Myre, 16; Hana St. Juliana, 14; and Justin Shilling, 17, authorities said. Justin died Wednesday morning at a hospital; the others died Tuesday, the sheriff’s office said. Tate died in a patrol car while a deputy was taking him to a hospital, Bouchard said. Anita’s Kitchen, where Shilling worked, shared a statement on social media about him. “Justin was an exemplary employee, a devoted friend and co-worker, co-captain of his bowling team, and simply a pleasure to be around. Our thoughts are with his family and friends at this difficult time,” the statement read. Seven others – six students and a teacher – were shot, Bouchard said. Among the wounded were a 14-year-old girl who was on a ventilator following surgery, Bouchard said Tuesday night. On Wednesday, it was announced she had been taken off the ventilator and was in stable condition. A 14-year-old boy had a gunshot wound to the jaw and head. The teacher, a 15-year-old boy and a 17-year-old boy were discharged, Bouchard said. Parents could face charges The attack was the deadliest US school shooting since eight students and two teachers were slain in May 2018 at Texas’ Santa Fe High School, according to a CNN tally. There have been 48 shootings this year on K-12 campuses, 32 of them since August 1. The suspect was being held at a juvenile detention facility. Bouchard said authorities asked a judge to transfer him from the detention facility to the Oakland County Jail. The judge agreed to the request. Charges of first-degree murder require allegations of premeditation, and evidence in this case indicates the shooting was planned “well before the incident,” McDonald said. This shooting was “absolutely premeditated,” McDonald told reporters, without elaborating. McDonald’s office will consider charges against the suspect’s parents, she said. The weapon authorities said was used in the shooting, a 9mm Sig Sauer SP2022 semiautomatic pistol, was purchased by Crumbley’s father on Friday, four days before shots rang out at the school, Bouchard said. Authorities are considering charges against both parents, with McDonald saying a decision would be made on that “swiftly.” The potential charges stem from the parents owning a gun. McDonald said that means securing it properly, ensuring ammunition is kept separate, among other legal responsibilities. “We have to hold individuals accountable who don’t do that,” she said. CNN has pressed the prosecutor to speak on whether evidence was recovered to support potential charges and which charges are being considered. The prosecutor declined to go into detail citing the investigation, but reiterated that an announcement would be made as soon as possible regarding whether charges would be brought. CNN has attempted to reach the parents of Ethan Crumbley and are attempting to identify an attorney for them. McDonald told CNN’s Erin Burnett on Wednesday she felt it was tragic how desensitized people were to gun violence, but gun owners should be held accountable for their ownership and possession of a firearm. Suspect and his parents met with school officials hours before shooting Bouchard said the 15-year-old had not been on law enforcement radar prior to the shooting. However, authorities did learn after the shooting that the suspect and his parents met with school officials a few hours before the shooting. Officials met with just the suspect the day before and with the suspect and parents the day of the shooting, Bouchard said. “The day before, it was a meeting with school personnel about some concerning behavior and the meeting the day of was with school personnel and parents about a different issue,” Bouchard said. The sheriff declined to go into issues on either day. “Prior to those two meetings there was no contact or nothing in his file by either concerning behavior or discipline,” he said. McDonald told CNN she was not able to comment on what, specifically, the gunman, parents and school officials discussed during their meeting. “There’s an additional piece of evidence that hasn’t been released yet, but I can assure you it was troubling, it was disturbing, and unfortunately he was allowed to go back to class,” she said. Video shows assailant ‘was shooting people at close range,’ sheriff says Investigators recovered more than 30 shell casings, said the sheriff, who’d earlier said at least a dozen rounds were fired. “We believe he fired at least 30 shots,” he said. Bouchard said two 15-round magazines were recovered by investigators and a third was recovered in the overnight hours. Investigators also learned the suspect had 18 rounds left, with seven in his pocket. “With this much ammunition still with him … the quick actions of the school and the lockdown as well as the deputies going to the danger, saved lives,” Bouchard said. Video from the school shows the assailant was “shooting people at close range – oftentimes toward the head or chest,” Bouchard told CNN’s “New Day” earlier Wednesday. “It’s chilling. It’s absolutely cold-hearted, murderous,” Bouchard said. Prosecutors said during Crumbley’s arraignment they’ve seen video from the school surveillance cameras showing Crumbley “methodically and deliberately” walking the hallways, aiming a gun at students and firing. “What is depicted on that video, honestly judge, I don’t have the words to describe how horrific that was,” said prosecutor Marc Keast. Video showed Crumbley with a backpack, and a minute later exiting the bathroom without the backpack and with a gun in hand, authorities said. He started firing right outside the bathroom, Keast said, but after children started running away, he continued to go down the hallway at a “methodical pace” and shot inside classrooms and at students who hadn’t had the opportunity to escape. This continued for another four or five minutes and he went to another bathroom, Keast said. When deputies arrived, he set down the gun and surrendered. “A preliminary review of the defendant’s social media accounts, his cellphone, as well as other documented evidence recovered on scene showed that this defendant planned this shooting, he deliberately brought the handgun that day with the intent to murder as many students as he could,” Keast said. Though much of the shooting was at close range, it nevertheless appeared “random,” Bouchard told CNN, without elaborating. The assailant “tried to breach classroom doors,” the sheriff said. “He actually fired through a number of the doors that I looked at last night – through the barricaded doors. … Some of those barricades were struck by gunfire,” Bouchard said. Bouchard praised the work of his deputies and other local law enforcement agencies that responded Tuesday, saying their coordination and active shooter training proved invaluable. Deputies were dispatched to the school at 12:52 p.m., and the suspect was in custody within three minutes of their arrival, Bouchard said. As deputies made their way through the school, they encountered the suspect, who then put his hands up, Bouchard said. Deputies took the gun and placed the suspect in custody. “I believe they literally saved lives, having taken down the suspect with a loaded firearm still in the building,” the sheriff said. ‘We believe we have some writings that contain his thoughts’ As for the investigation into a motive: “We believe we have some writings that contain some of his thoughts,” Bouchard said, adding he didn’t immediately know whether the writings reveal intent. Investigators executed a search warrant at the suspect’s home and have searched the school, he said. Authorities seized a phone and are examining other seized items. Michigan law prevents police from talking to a juvenile without parental permission, and the parents have refused that permission and requested a lawyer, Bouchard said. “So, we can’t get the motive from the suspect that we have in custody, but we think we’ve got a path to get a lot of supportive information as to how and why this occurred. We’ve recovered some evidence that we’re now beginning to pore over,” Bouchard said. Authorities also are investigating pictures of a target and the weapon posted on social media by the suspect, he added. ‘I’m going to text my family, say I love them’ As hundreds of law enforcement officers swarmed the campus Tuesday, students and teachers relied on tactics they’d learned in active shooter drills to protect themselves. “This district has been very good in training their personnel and their students on active shooters,” Undersheriff Michael McCabe said. Kluska’s teacher, Moises Cortez, jumped into action after a lockdown was announced over the school’s loudspeakers, said the student who recorded video of his classmates escaping through a window. “He shut the door and put, like, a metal doorstopper so no one would be able to kick in the door.” Kluska told CNN. “After he turned off the lights, he told us to get to the corner because this might not be a drill and he wants to be safe.” People were injured as they rushed out of the school, Bouchard said. Most were treated and released at a nearby staging area. Zander Cumbey, a junior at the high school, told CNN’s Victor Blackwell that he started hearing screams about a minute after he sat down in his classroom. “I heard screams come from the hallway and then the first gunshot happened, and my teacher, he walked into the classroom, he locked the door and he told us to call 911,” Zander said. “And then we heard the rest of the gunshots go off, more screams.” He said as he was on the phone with dispatchers, he didn’t really speak to them. “I just said kind of said ‘Oxford High School, shooter’, because I couldn’t talk,” Zander said. He texted his parents that he loved them, he said, and texted his younger brother who also attends the school to see whether he was safe. Zander told CNN one of the victims – Tate Myre – was a close friend who was on the football team with him. Donna Sanders’ youngest grandchild was changing classes when he heard gunshots, she told CNN. He and others ran through an exit door and went to a nearby grocery store to escape, he told her. “He was able to run to safety with others while his brother was trapped inside,” Sanders said. Sanders’ daughter, Vontysha Pittman, said her oldest son sought safety in a classroom with a teacher and other students. He hid under a desk and called his father to tell him what was happening, she said. “They are both are safe at home, but they are broken. We need prayers and not just for us but all the families at Oxford,” Sanders said. Page’s classroom was in lockdown for an hour, the senior told CNN. The entire experience as “insane” as he contemplated whether he would live through the ordeal. “The very first thing in my head was, ‘Is this actually happening? I’m going to text my family, say I love them just in case, if I were to die.’ Then when everything calmed down for a second, I was able to catch my breath and rationalize things,” he said.