Many who knew him were baffled by Thursday's attack.
The only signs of trouble from Kazmierczak came in the weeks leading up to Thursday's shooting. The 27-year-old had become erratic after he stopped taking his medication. What the medication was for, law enforcement authorities would not say.
In the latest reports, however, a former employee at a Chicago psychiatric treatment centre told The Associated Press that Kazmierczak was placed there after high school by his parents. She said he used to cut himself and had resisted taking his medications.
Last September, he worked as an officer at the Rockville Correctional Facility in Indiana. But after two weeks, he failed to show up on the last day of training and never returned. He was also in the army for about six months in 2001-02, but he told a friend he'd gotten a psychological discharge, according to AP.
As more investigation is underway, six white crosses have been placed on a snow-covered hill around the center of the NIU campus. The crosses bear the names of the five victims - Daniel Parmenter, Ryanne Mace, Julianna Gehant, Catalina Garcia and Gayle Dubowski - and the gunman.
"Let me say that their (families of victims) response, as you can imagine, is heart-rending, but I was impressed with their internal strength," NIU president Dr John Peters said Friday. "They will get through this with our help and the help and prayers of a lot of individuals across this country and the world."
The campus remains closed and a reopening date will be announced, Peters said.
"But first, we really have to deal with this healing process," he said. "Let me say to our community, to the NIU community, parents, victims and students, faculty and staff, we will get through this together."
Candlelight prayer vigils have lit the campus in the evenings, with Christian students seeking to have a presence on campus during a time of grief.
"We are deeply saddened by such events on our American campuses," said InterVarsity president Alec Hill, "and we ask God to guide our [InterVarsity Christian] Fellowship in bringing the life of Jesus Christ to colleges and universities."
