DEKALB, Illinois (CNN) -- A firearms dealer in Green Bay, Wisconsin, Friday confirmed a bizarre link between the graduate student accused of killing five people at Northern Illinois University and the gunman in last year's deadly shootings at Virginia Tech.
A Web site used to buy gun accessories by Steven Kazmierczak is owned by the same company that operates a site patronized by Seung-Hui Cho, the company said.
Kazmierczak ordered two 9 mm Glock magazines and a holster for a Glock handgun from the Web site February 4, said a statement released by TGSCOM Inc.
He received them February 12, two days before the NIU shootings, it said.
"TGSCOM Inc. also operates the Web site used by Seung-Hui [Cho] to purchase a firearm used in the Virginia Tech shootings last April," the statement said.
Cho killed 32 people before turning a gun on himself in that incident. Watch witnesses say they're in shock »
TGSCOM Inc. said it is assisting law enforcement in the investigation.
Meanwhile, investigators searched a room at a DeKalb, Illinois, hotel Friday in connection with the deadly shooting, a source close to the investigation said.
Police had been looking for a laptop computer, and one was found in the room and turned over to investigators, DeKalb Travelodge manager Jay Patel told CNN.
A bomb squad also swept the room for explosives, according to the source.
Earlier, Northern Illinois University's police chief described Kazmierczak as "an outstanding student" who reportedly stopped taking medication recently and became "somewhat erratic."
Kazmierczak of Champaign, Illinois, opened fire on a geology class Thursday, shooting 21 people before killing himself. Five people were killed in addition to the shooter.
All the victims were from Illinois. The DeKalb County coroner's office identified four of them: Daniel Parmenter, 20, of Westchester; Catalina Garcia, 20, of Cicero; Ryanne Mace, 19, of Carpentersville; and Julianna Gehant, 32, of Meriden. See photos of the victims »
The fifth victim, Gayle Dubowski, 20, of Carol Stream, died at a hospital in Rockford and was identified by Winnebago County authorities.
Three people remained in critical condition Friday afternoon.
University Police Chief Donald Grady said people close to Kazmierczak have told authorities he was taking medication but had stopped and had become "somewhat erratic" in the last couple of weeks.
Grady would not name the medication Kazmierczak had been using or the condition for which he was taking it.
He said investigators had not determined a motive and are not aware of any relationships the gunman may have had with anyone in the class where the shooting occurred. Nor did Kazmierczak have any previous contact with police, Grady said. Watch Grady detail the shooter's profile »
"There were no red flags," Grady said. "He was an outstanding student, he was an awarded student, he was someone that was revered by the faculty, staff and students alike. ... So we had no indications at all."
Kazmierczak used a shotgun hidden in a guitar case and three handguns hidden under a coat, Grady said.
Grady said he didn't know how many shots had been fired, but he said investigators recovered 48 bullet casings and six spent shotgun shells.
The federal Bureau of Alcohol, Tobacco, Firearms and Explosives said all four weapons were bought at a gun store in Champaign.
Kazmierczak bought a Remington 48 shotgun and a Glock handgun Saturday, ATF spokesman Tom Ahearn said.
He bought a High Point .380-caliber handgun December 30 and a Sig Sauer 9 mm handgun in August.
The timing of weapons purchases could be significant in considering how long the shooter had been planning his spree.
Champaign police recovered at least one weapon from Kazmierczak's apartment Thursday night after being admitted by his girlfriend, Chief R.T. Finney said.
Authorities in Polk County, Florida, said police in Illinois had them question the man's father, Robert Kazmierczak of Lakeland, Florida.
A tearful Robert Kazmierczak stepped onto his porch and asked reporters to go away Friday. Watch the father break down »
University President John Peters said the gunman was a former graduate student who had a good record as an undergraduate, receiving a degree in sociology at the school in 2006. Watch Peters reflect on the victims' families »
"There's no indication that there was any trouble," Peters said.
President Bush Friday asked Americans "to offer their blessings -- blessings of comfort and blessings of strength" to the community at Northern Illinois University in DeKalb, about 65 miles west of downtown Chicago.
All classes and events on the university campus were canceled until further notice. Dormitories remained open to house and feed students.
"I know what's happened, but I don't want to believe it," said Stefanie Miller, who saw two of her friends die in the Cole Hall shooting. Watch the shocked student ask for prayers »
Tributes were surfacing online. A Facebook community called "Pray for Northern Illinois University Students and Families" had more than 51,000 members by midday Friday. See photos of the campus in mourning »
Gunman 'just started shooting'
About 160 students were registered in the class that met in the large lecture hall.
Kevin McEnery said he was in the classroom when the gunman, dressed in a black shirt, dark pants and black hat, burst in carrying a shotgun.
"He just kicked the door open, just started shooting," McEnery said. "All I really heard was just people screaming, yelling 'get out.' ... Close to 30 shots were fired." See a map of where the shooting took place »
Student Zach Seward said, "We were having lecture as normal, a PowerPoint presentation. All of a sudden the side door on the stage opens. Average-height male Caucasian comes out, draws a shotgun, pumps it and fires the first round on the first couple of rows.
"After that, everybody ducked down, started screaming, going toward the door. On the way out, I heard shots still being fired. Everybody was screaming and running out of the room. It was chaos." Watch Seward describe the chaos »
The shooting began at 3:06 p.m., and in less than a minute there were two university police officers "in the area of the scene," Grady said.
Soon there were eight officers on the scene, he said, adding that the response "was immediate."
At 3:20, an all-campus alert went out via the school Web site, e-mail, voice mail, the campus crisis hot line, the news media and alarm systems, he said.
By 4 p.m., DeKalb police had swept the area "and determined there was only one gunman" and that he was dead, Peters said.
While authorities said they responded within seconds to Thursday's incident, they also vowed to see what might have been done better.
"If there is a way where this tragedy could have been anticipated, or stopped beforehand, we will find it," said Illinois Gov. Rod Blagojevich.
He ordered flags flown at half-staff throughout the state.
Security around campus was increased in December when police found threats scrawled on a campus bathroom wall that included racial slurs and references to last April's Virginia Tech shootings.
Peters and Grady said no evidence points to a link between the December incident and Thursday's shooting.
The university revised its emergency procedures after the Virginia Tech massacre, Peters said.
"I believe that paid off," he said. "That's really a sad thing to say, that you have to learn from an event like that, but we knew how we wanted to communicate and we sort of had some messages prearranged, and we got out there fairly quickly."
Meanwhile, the president of Virginia Tech expressed his "shock and horror" about Thursday's shooting.
"We would like to think that institutions of learning and of rational thought would be spared such madness. Sadly, this is not the case in today's world," Charles Steger wrote in a letter to Peters.
Northern Illinois University has an enrollment of more than 25,000. The campus covers 755 acres. E-mail to a friend
CNN's Kevin Bohn contributed to this report.