DEKALB Ill.

A man dressed in black opened fire with a shotgun and two handguns from the stage of a lecture hall at Northern Illinois University on Thursday, killing five students and injuring 16 others before committing suicide, authorities said.

The gunman fatally shot four women and a man in a "brief, rapid-fire assault" that sent terrified students running for cover, university President John Peters said. Four of the six total dead died at the scene, and the other two died at a hospital, he said.

Witnesses in the geology class said "someone dressed in black came out from behind a screen in front of the classroom and opened fire with a shotgun," Peters said.

Lauren Carr said she was sitting in the third row of the lecture hall around 3 p.m. 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.'"

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, adding that police had no apparent motive.

Seventeen victims were brought to Kishwaukee Community Hospital in DeKalb, according to spokeswoman Theresa Komitas. One died, two were admitted and three were discharged; five are being evaluated and six others were transferred to other hospitals in critical condition. At least one male died at OSF St. Anthony Medical Center in Rockford, an official said.

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."