A day after [article id="1581631"]27-year-old gunman Steven Kazmierczak opened fire[/article] inside a lecture hall at Northern Illinois University in DeKalb, Illinois -- shooting 21 people and killing six, including himself -- officials said that he had become "erratic" in recent weeks after he stopped taking medication and fired more than 50 shots, and perhaps more, before taking his own life.

(At press time, CNN had revised the total number of fatalities from seven to six.)

Noting how quickly the shootings took place, NIU police chief Donald Grady said at a press conference Friday (February 15) that the event began around 3:06 p.m. CT. Less than 30 seconds later, the first two officers were in the area, and within 90 seconds, eight more officers were on site, all of them entering the hall immediately upon arrival.

"Within that short period of time, the shooter walked into the building, managed to begin his shooting spree and conclude it before we were able to actually enter the building and stop it," Grady said. He also said that Kazmierczak, who was from the Champaign-Urbana area in Illinois, had four guns with him during the rampage, including two 9mm handguns, another handgun and a Remington shotgun, which he reloaded during the spree.

Grady said there is no known motive as of yet, no notes indicating why Kazmierczak returned to the campus more than nine months after leaving it, no connection as yet to anyone in the hall and no "red flags" to indicate why he opened fire. He described Kazmierczak as an "outstanding student" who was admired by the faculty and students who knew him, and there were "no indications" that he was the type of person who would engage in this kind of violence.

He did note that Kazmierczak had been taking an unspecified medication and that people close to the shooter said he had stopped taking it recently and had become "somewhat erratic" over the past few weeks. Grady added that there was nothing in his background that would have prevented Kazmierczak from owning guns, and that he had legally purchased two of the handguns from a firearms dealer in Champaign-Urbana on February 9. Police are still looking into the background of the other two weapons.

NIU President John Peters said during a news conference that the university had a plan in place for just this kind of incident and that it had been practiced repeatedly and was executed exactly as intended during the chaotic minutes after Kazmierczak began his rampage. "We were dealing with a disturbed individual who intended to do harm on this campus," said Peters. "We did everything we could to ensure the safety of this university."

Kazmierczak, dressed all in black and carrying a shotgun and three handguns, kicked open the door of the 200-seat lecture hall and opened fire, shooting students as they attempted to flee the chaotic scene. Grady said Kazmierczak hid the shotgun he used in the attack in a guitar case and three handguns under his coat and that, so far, 48 shell casings and six shotgun shells have been found on the scene. CNN reported that authorities in Polk County, Florida, had been asked by Illinois police to question the man's father, Robert Kazmierczak of Lakeland, Florida, in the wake of the shootings, but no information was available at press time about what may have come of that interview.

Less than a year after a mentally unstable gunman killed 32 students on the campus of [article id="1557156"] Virginia Tech University[/article], raising questions about how students are alerted to threats on campus, authorities were quick to praise NIU for its swift dissemination of information on Thursday's incident. NIU updated its security and student-alert system after the Virginia Tech shootings and, according to reports, a campus-wide alert went out by 3:20 p.m. confirming the presence of a shooter on campus, though without a mention of any deaths, and the campus went on lockdown soon after the first reports of shooting came in. By 4 p.m. an "all clear" message was distributed to all students and faculty.

Peters said discussions have already begun about how best to honor the memories of the students who were killed. A candlelight vigil will be held on the campus' Martin Luther King Jr. Commons Friday night, and Peters said he would announce plans for reopening the campus at a later date. The NIU campus was placed on a security alert in December after police found threats with racial slurs in them scrawled on a bathroom wall that made reference to the Virginia Tech shootings with a warning that "things will change most hastily" in the semester's final days. Peters said Thursday that he did not believe the shootings were related to those threats. As of Friday morning, a Facebook community page titled "Pray for Northern Illinois University Students and Families" had already registered nearly 55,000 members.

On Friday afternoon, Illinois Governor Rod Blagojevich visited the NIU campus and called Thursday's shooting "a terrible act of unthinkable horror." Blagojevich said he wanted to visit the school to personally express his condolences to the entire academic community. During a press conference, the governor said police are looking into what may have motivated the killer. He also vowed to ensure that all of the state's colleges and universities are kept in the know, and urged all schools to update their own safety plans.

The incident at NIU was the fifth U.S. school shooting in as many months, following incidents in Ohio in October, where 14-year-old Asa Coon injured two students and two teachers before killing himself; in Louisiana two weeks ago, where a nursing student killed two women and herself at Louisiana Technical College; in Tennessee on Monday, where a 17-year-old is accused of shooting and critically wounded a fellow student; and on Thursday, Ventura County prosecutors charged a 14-year-old with the shooting death of a classmate, labeling the killing of the Oxnard, California, teen a premeditated hate crime, according to the Los Angeles Times. Brandon McInerney was charged as an adult in the murder of Lawrence King, 15, who classmates said had recently come out as being gay and had gotten into a verbal confrontation with McInerney and several other students the day before his Tuesday murder. King was declared brain-dead and was expected to be taken off a ventilator late Thursday night.

[This story was originally published at 12:05 p.m. ET on 02.15.2008]