Expert: 'We may never know what really happened'

What makes an award-winning student open fire in a crowded lecture hall, kill five students, injure 18 others, then take his own life?

Experts say police most likely will discover 27-year-old Steven P. Kazmierczak suffered from delusions and paranoia, that he suddenly withdrew from society and decided to take his own life in a most dramatic fashion.

Greg McCrary, a retired FBI special agent expert in violent crime analysis, said it's a myth someone "snaps." Instead, 67 percent of mass murderers and school shooters suffer from a mental illness which, more than likely, triggered the shootings.

McCrary said it takes careful thinking from someone with serious mental health issues to carry out a plan like the one that unfolded Thursday at Cole Hall on the Northern Illinois University campus.

More likely, he said, when the shooter went off his psychological medication, weeks and months of delusions raced through his head. That was followed by paranoia that caused him to slowly withdraw from society.

"No one is normal one day then does something like this. This is a long process that took place over a long time," McCrary said Friday. "(Mass murderers) become paranoid and delusional over a period of time, but it's not seen because the person withdraws from society."

Police have not said what medication the gunman stopped taking in the weeks before the shootings. Also, McCrary said he has not seen the situation firsthand and does not know intricate details of the case.

However, the 25-year veteran special agent of the FBI's behavioral science unit said the shooter probably was looking to commit suicide. As in many other cases, he added, they often "tragically decide to take others with them."

"I'm sure police will discover he was isolated, resentful and became alienated from society," he said. "His mind deteriorated while off the medications; he became paranoid and then made a predetermined decision to do this."

In the end, McCrary said, it will be a long time before friends and relatives discover the missed signals of deteriorating mental health.

"We may never know what really happened," he said. "The FBI and police will work to fill in these blanks to determine what triggered this. But it'll be a long period of things that people didn't catch."