Word of the ambush attack inside a lecture hall at Northern Illinois University on Thursday sent panic throughout the sprawling campus.

Jerry Santoni was in a back row of the hall when he saw a man walk onto the stage and open fire.

"I saw him shoot one round at the teacher," Santoni said. "After that, I proceeded to get down as fast as I could."

Santoni dived down, hitting his head on the seat in front of him with such violence that it left a knot on his forehead. Then he fled Cole Hall.

Authorities said the intruder, a former student wielding a shotgun and two handguns, killed five people and wounded more than a dozen others before killing himself.

Senior Ashley Dallman said she was in an acting class in a neighboring building when several students from Cole Hall came running in. Her professors locked the doors and they listened to news reports on the radio for about an hour before school officials told them they could leave.

"We all started crying," she said. "We didn't know what to do. It was a very intense moment."

Police said they got to the hall within two minutes of the 3 p.m. shooting. Alan Edrinn, 21, a journalism major from Matteson, Ill., arrived outside Cole Hall a half hour later.

"It was very chaotic. People were definitely in a panic," Edrinn said. "I saw bodies on the sidewalk, it looked like two, people were attending to them."

The campus was eerily quiet Thursday night. All the lights were on in the library -- about 200 yards from the crime-scene tape that surrounded Cole Hall -- but the seats inside sat empty.

Fliers offering counseling services were posted around campus residence halls, where puffy-eyed students pulled luggage for trips home and kept their cell phones close at hand.

Mike MacQueen's phone brought no comfort.

"I just got a text message that a friend of mine passed away," the 20-year-old from Elmhurst said. "He was a good person, he didn't deserve to die."

"It's surreal, this happening so close to home," he said.

Tracy Knuth, a 23-year-old senior, saw dozens of ambulances swarm onto the scene. "Everyone is completely and utterly freaked out," Knuth said by phone from her apartment.

Knuth said a large number of courses are taught at Cole Hall, from undergraduate math and science to liberal arts courses; she said the hall has two or three large lecture auditoriums that can each accommodate about 500 students.

"Everyone is scared to go to classes next week," she said.

All classes were canceled Thursday night and the 25,000-student campus was closed on Friday.

Freshman Monica DeFrancesco initially thought about heading home to her parents' house after the shooting, but decided to stay in her dorm room in Douglas Hall, a 10-minute walk from Cole Hall.

"There's a lot of security," said DeFrancesco, who didn't see the shootings or know anyone involved. "They're checking your bags and your IDs ... I feel very comfortable."