Virginia Tech gunman Cho Seung-hui was a moody loner who took antidepressants and wrote gory fiction, news reports say. But nobody could have predicted from this that he would commit violent acts, experts tell WebMD.

Officials have identified Cho, 23, as the gunman who Monday shot and killed 32 people on the Virginia Tech campus.

"When a tragedy like this happens, we want to know how to defend ourselves and our families. We are very eager to see this as a gross aberration that might have identifiable warning signs," Jeff Victoroff, MD, tells WebMD.

But that simply isn't the case, says Victoroff, an associate professor at the University of Southern California and an expert on human aggression and the neurobiology of violence. People like Cho have, throughout history, appeared without warning in every human culture.

"It is true that people like Mr. Cho and the Columbine shooters exhibited some aberrant behaviors that, with 20-20 hindsight, might have tipped off sensitive observers," Victoroff says. "But we don't usually attend to those warning signs because they are so common among adolescents. ... We will never be altogether safe from such people."

Unless they have previously acted violently or threatened violence, there's simply no way to predict whether a person will commit a violent act, says Robert Irvin, MD, medical director of a long-term residential treatment program that is part of the Bipolar and Psychotic Disorders Program at Harvard's McLean Hospital in Belmont, Mass.

"The greatest predictor of acts of violence is prior acts of violence. Lacking that, we cannot say who will be violent and who will not," Irvin tells WebMD. "There is no reliable predictor of who or who not to avoid. Because that quiet, lonely person who is not so verbal may be very fearful himself and the least harmful person in the world."

Mental Illness, Antidepressants, and Violence

Could the antidepressants that Cho was said to have been taking made him violent? No, Irvin says.

It's not known whether Cho was taking antidepressants under a doctor's supervision, whether he was taking the medications properly, and whether he was taking some drug other than antidepressants.

"Certainly just being on an antidepressant does not increase your risk of engaging in violence," Irvin says. "Antidepressants causing increased risk of self-harm have been talked about, but there is much more evidence to support that they are effective in treating depression. The risk of self-harm is much greater when patients are left untreated."

Might underlying depression be to blame? Probably not.

"People who are hopeless, who don't experience any joy or happiness, their thoughts are far more likely to tend toward self-harm than harm to anyone else," Irvin says. "If they are moved to violence, they are far and away more frequently the victims."

There is a form of depression -- some think it a form of psychosis -- which doctors call "major depression with psychotic features." People with this kind of depression have delusional thinking -- such as believing everybody at their workplace is very clearly out to get them, perhaps by putting bugs in their offices in order to control them.

"If you are paranoid, perceiving you are threatened when you are not, you might be prone to violence," Irvin says. "But these are people who, if given a choice, would hurt themselves or flee before acting in an aggressive way toward others."

Victoroff agrees that paranoid individuals are more prone than others to commit violence.

"Someone who has a grossly distorted threat-perception system is more likely to commit violent acts," he says. "Humans respond to threat by flight or by fight. Those predisposed to respond with fight, who regard innocent people all around them as terribly threatening to them, will be prone to harm those innocent people."

Even so, Victoroff says, the majority of people suffering paranoia do not commit violent acts, so it's impossible to say whether a particular paranoid man or woman will become violent.

We tend to think that only mentally ill people would commit horrific crimes. But this may be false reassurance, Irvin says.

"One of the reasons we try to understand this aberrant behavior in terms of an illness is that it gives us a sense we can identify these people ahead of time. But just because the act is crazy does not mean the person suffered from a defined psychiatric illness," he says. "It is an ongoing debate whether these people need to be dealt with in the criminal justice system or the mental health system."

That's because there are two basic forms of violence: sudden, impulsive acts of aggression and premeditated violent acts.

"Premeditated aggression enters the realm of pathologic sociopathy -- and there is no good known treatment for sociopaths," Irvin says.

Cho's Violent Fiction

But shouldn't Cho's violent fiction have sounded an alarm? The Chicago Tribune reports that a creative writing teacher was so disturbed by Cho's writing assignments that she referred him to a counseling center.

The Tribune quotes a fellow student as saying that Cho wrote a play in which a boy violently suffocates his stepfather with a Rice Krispies treat.

Writing students do often write frightening things, says Carol Lee Lorenzo, an author and fiction teacher at Atlanta's Callanwolde Fine Arts Center. Where students cross the line, she says, is when they write about actual experiences. In such cases, she says, she returns the assignment and asks the student to justify the violence in terms of the story they are telling.

In her 20 years of teaching fiction writing, Lorenzo says she's never referred a student for counseling.

"Writers reveal things in fiction that are not autobiographical, but are part of our own deep mysteries we are trying to explore," she says. "This does not mean we take these impulses all the way as our characters do. But we have to explore that, or why would anybody read anything we write?"

Perhaps Lorenzo comes close to the terrible truths behind Cho's crime when she talks about why writers describe violent acts.

"Writers are often scared of what is not spoken. So sometimes writers will work with violent things that are expressive of the deep, dark, unfulfilled emotional experience of their lives," she says. "What scares us is this: What if it does become fulfilled in real life by not being expressed in fiction?"

Perhaps this is what happened to Cho.

"We should be more scared of the potential of the human personality than of meeting a grizzly bear in the woods," Lorenzo says. "We are so capable of violence, and yet we have these wonderful controls. If you don't look down at the deep, rich, dark mysteries inside you, you are an even scarier person because it can jump up on you without warning."

This article was reviewed by Louise Chang, MD.

SOURCES: Robert Irvin, MD, medical director, Appleton Continuing Care Program, Bipolar and Psychotic Disorders Program, McLean Hospital, Belmont, Mass.Jeff Victoroff, MD, associate professor of clinical neurology and psychiatry, University of Southern California; editor,Tangled Roots: Social and Psychological Factors in the Genesis of Terrorism. Carol Lee Lorenzo, fiction teacher, Callanwolde Fine Arts Center, Atlanta; author, Nervous Dancer.