DEKALB, Ill. — A former student dressed in black walked onto the stage of a lecture hall at Northern Illinois University and opened fire on a packed science class yesterday, killing five students, wounding 16 and setting off a panicked stampede before committing suicide.

Police say they know of no motive for the rapid-fire assault, carried out by the gunman who fired indiscriminately into the crowd with a shotgun and two handguns as students dove to the floor and ran toward the exit. At least two of the wounded were hospitalized in critical condition.

"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."

TEACHER WOUNDED

University President John Peters said three students and the gunman died at the scene, and two other students died at a hospital.

The teacher, a graduate student, was wounded but was expected to recover.

Peters said the gunman was a former graduate student in sociology at NIU, but was not currently enrolled at the 25,000-student campus about 65 miles west of Chicago.

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

Witnesses said the skinny gunman, dressed in black and wearing a stocking cap, emerged from behind a screen on the stage of 200-seat Cole Hall and opened fire just as the class was about to end around 3 p.m. Officials said 162 students were registered for the class but it was unknown how many were there yesterday.

Lauren Carr said she was sitting in the third row when she saw the shooter walk through a door on the right-hand side of the stage, pointing a gun straight ahead.

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

She said a student in front of her was bleeding, "but he just kept running."

"I heard this girl scream, 'Run, he's reloading the gun.' "

Student Jerry Santoni was in a back row when he saw the gunman enter a service door to the stage.

"I saw him shoot one round at the teacher," he 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, leaving a knot about half the size of a pingpong ball on his forehead.

Michael Gentile was meeting with two of his students directly beneath the lecture hall when the shootings happened. He could hear the chaos a few feet above his head.

"The shotgun blast must have been so loud," said Gentile, a 27-year-old media studies instructor. "It sounded like something was dropping down the stairs ... We had no idea what this was."

Then, shorter, sharper noises he recognized as handgun shots.

"There was a pretty quick succession ... just pow, pow, pow," said Gentile, who didn't leave his office for about 90 minutes. He used a surveillance camera just outside his office to confirm that the people knocking on his door were police.

George Gaynor, a senior geography student, who was in Cole Hall when the shooting happened, told the student newspaper the Northern Star that the shooter was "a skinny white guy with a stocking cap on."

He described the scene immediately following the incident as terrifying and chaotic.

"Some girl got hit in the eye, a guy got hit in the leg," Gaynor said outside just minutes after the shooting occurred. "It was like five minutes before class ended too."

STUDENTS TARGETED

Witnesses said the young man carried a shotgun and a pistol. Student Edward Robinson told WLS that the gunman appeared to target students in one part of the lecture hall.

"It was almost like he knew who he wanted to shoot," Robinson said.

"He knew who and where he wanted to be firing at."

All classes were canceled last night and the campus was closed today.

The school was closed for one day during final exam week in December after campus police found threats, including racial slurs and references to shootings earlier in the year at Virginia Tech, scrawled on a bathroom wall in a dormitory. Peters said he knew of no connection between that incident and yesterday's attack.

The shooting was the fourth at a U.S. school within a week.

On Feb. 8, a woman shot two fellow students to death before committing suicide at Louisiana Technical College in Baton Rouge.

In Memphis, Tenn., a 17-year-old is accused of shooting and critically wounding a fellow student Monday during a high school gym class, and the 15-year-old victim of a shooting at an Oxnard, Calif., junior high school has been declared brain dead.

Associated Press writers Carla K. Johnson, Michael Tarm, David Mercer, Martha Irvine, Nguyen Huy Vu, Sarah Rafi and Mike Robinson contributed to this report.