Florida authorities and a university official have identified the gunman in the Northern Illinois University slayings as 27-year-old former student Steven Kazmierczak, though police have yet to release a name. 

Seven people have died following Thursday's massacre at Northern Illinois University.

Police are still trying to determine a motive after a sociology student who graduated last spring returned to the school, entered a lecture hall with a shotgun and two handguns and opened fire at about 3pm. He killed five people and wounded 16 others, some critically, before fatally shooting himself. One of those critically injured victims succumbed to their wounds overnight.

According to school officials the gunman, who hasn't been identified, didn't have a criminal record. Polk County, Florida sheriff's officials said they were asked to speak with "the father of the shooting suspect," a man who lives in Lakeland, Fla., and was identified as Robert Kazmierczack.

"I kept thinking, 'Oh God, he's going to shoot me. Oh God, I'm dead. I'm dead. I'm dead,'" said Desiree Smith, a senior journalism major who dropped to the floor near the back of the auditorium.

"People were crawling on each other, trampling each other," she said. "As I got near the door, I got up and I started running."

University President John Peters said four people died at the scene including three students and the gunman, while three more have since died in hospital. The teacher, a graduate student, was hurt but expected to recover. The gunman, dressed in black and wearing a stocking cap, wasn't currently enrolled at the school, which has 25,000 students and is located 65 miles west of Chicago.

"It appears he may have been a student somewhere else," University Police Chief Donald Grady said.

No other details have been released about the gunman or the victims.

Student Lauren Carr was sitting in the third row of the lecture hall when she saw the shooter walk through a door by the stage.

"I personally Army-crawled halfway up the aisle," the 20-year-old sophomore recalled. "I said I could get up and run or I could die here."

The school was locked down within 20 minutes of the shots, part of a security plan created after a student at Virginia Tech killed 32 people last year.

Classes were cancelled Thursday night and the campus was closed Friday. It's the fourth school shooting in the U.S. within a week.

On Feb. 8 a woman shot two fellow pupils to death before killing herself at Louisiana Technical College in Baton Rouge. This past Monday a 17-year-old was accused of shooting and critically wounding a fellow student in gym class at a Memphis, Tenn. high school. And a 15-year-old has been declared brain dead after being shot at a junior high school in Oxnard, Calif.

With files from Associated Press