The man who gunned down five people at Northern Illinois University in a suicidal rampage had recently ”become erratic” after halting his medication and carried a shotgun to campus inside a guitar case, police said Friday.

The man, 27-year-old former student Stephen Kazmierczak, was also wielding three handguns during Thursday’s attack inside a lecture hall. At least some of the weapons were purchased legally less than a week ago, on Feb. 9, authorities said.

Campus Police Chief Donald Grady said investigators have recovered 48 shell casings and six shotgun shells following Thursday’s attack. The gunman paused to reload his shotgun after opening fire on a crowd of terrified students in a geology class.

Kazmierczak, whose first name was earlier listed as Steven, was taking an unspecified medication, Grady said.

”He had stopped taking medication and become somewhat erratic in the last couple of weeks,” Grady said, declining to name the drug or provide other details.

The gunman wounded 15 people in Thursday’s attack, which sent panicked students fleeing for the exits.

”There is no note or threat that I know of,” NIU President John Peters said on Friday ABC’s ”Good Morning America.” ”By all accounts that we can tell right now (he) was a very good student that the professors thought well of.”

The shooter had been a graduate student in sociology at Northern Illinois as recently as spring 2007, but was not currently enrolled at the 25,000-student campus, Peters said. He also said the gunman had no record of police contact or an arrest record while attending the university, about 65 miles west of Chicago.

He was currently enrolled as a graduate student at the University of Illinois at Urbana-Champaign, said NIU spokeswoman Melanie Magara.

DeKalb County Coroner Dennis J. Miller released the identities of the four victims who died in his county: Daniel Parmenter, 20, of Westchester; Catalina Garcia, 20, of Cicero; Ryanne Mace, 19, of Carpentersville; and Julianna Gehant, 32, of Meridan.

Two other victims died after being transferred to hospitals in other counties, Miller said. Winnebago County Coroner Sue Fiduccia said a female victim died in her jurisdiction but has not been identified pending notification of family.

Witnesses said the 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 Thursday.

Allyse Jerome, 19, a sophomore from Schaumburg, said the gunman burst through a stage door and pulled out a gun.

”Honestly, at first everyone thought it was a joke,” Jerome said. Everyone hit the floor, she said. Then she got up and ran, but tripped. She said she felt like ”an open target.”

”He could’ve decided to get me,” Jerome said. ”I thought for sure he was gonna get me.”

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!”’

More than a hundred students cried and hugged as they gathered outside the Phi Kappa Alpha house early Friday to remember Parmenter, the 20-year-old sophomore from Elmhurst, who was one of those killed.

”I’m not angry,” his stepfather, Robert Greer, told the Tribune. ”I’m just sad, and I know that right now what I need to do is comfort my wife.”

The campus was closed on Friday. Students were urged to call their parents ”as soon as possible” and were offered counseling at any residence hall, according to the school Web site.

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. Police determined after an investigation that there was no imminent threat and the campus was reopened. Peters said he knew of no connection between that incident and Thursday’s attack.