The Anatomy of Violence

It is a specific kind of paranoia: a tendency to blame everyone but themselves for their troubles, to believe the world is against them and life is unfair. "They see others as being responsible for their problems; it's never their fault," says James Alan Fox, professor of criminal justice at Northeastern University. "That's why when they come to the decision that life isn't worth living, they decide to take others with them. That's who they hold responsible." In the video he mailed to NBC, Cho rants that "you forced me into a corner and gave me only one option ... Now you have blood on your hands that will never wash off." Suggesting counseling is often fruitless. "The response is, 'Counselor? Therapist? I'm the only sane person on campus'," says sociologist Jack Levin of Northeastern, who last year gave a lecture at Virginia Tech on mass murderers. "They've become so estranged from society, there's nothing you can do short of putting them involuntarily in a psychiatric hospital."

Some mass murderers may be trying to exercise power over a world they believe has left them powerless. "They often feel some great injustice has been done to them. They're angry and they want to take it out on the world," says Schlesinger. "They develop the idea that murder will be the solution to whatever their problem is, and they fixate on it." The problems can range from loss of a job (many office shootings are committed by resentful ex-employees) to a financial setback to a bad breakup. But while such travails may push the killer over the edge, he was teetering there in the first place as a result of a long string of perceived insults, hardships and failed relationships. "You don't just get a D on your report card and then open fire on 30 people," says Levin. "It takes a prolonged series of frustrations. These people are chronically depressed and miserable."

That raises the question of where the misery and the ensuing hatred, resentment and anger come from. An obvious place to look is early childhood. Studies find that up to 45 percent of boys who commit serious violent crimes by the age of 17, and up to 69 percent of girls, were inappropriately aggressive in childhood, picking fights with other kids. It is very rare for violence to show itself for the first time in a person's 20s. (It doesn't work the other way, however. Most aggressive youths mellow out and do not become violent adults, probably because circuits such as those that underlie judgment and impulse control become fully developed only in a person's late teens or early 20s.)

But the link between childhood aggression and later violence is not simply that aggression begets aggression. Instead, an aggressive child, a child with poor impulse control or pathological shyness or even an inability to read other kids' tone of voice elicits certain behaviors and treatment from peers and parents. An odd child cannot make friends. His quirks drive away other kids. He tries his parents' patience and love. This back-and-forth between innate tendencies—blame them on genes or on brain wiring, it doesn't matter—magnifies the problematic temperament or behavior and sculpts a psyche that hurtles toward criminal violence. A 2006 study of 334 adolescents found that boys who showed reactive aggression at age 7 had become, by age 16, impulsive, hostile, socially anxious and friendless. Cho was so isolated he barely spoke to roommates, and in the ranting video he sent to NBC, he snarls, "You have vandalized my heart, raped my soul and torched my conscience."

Like the discovery that gene expression can depend on the environment, and that brain circuitry reflects life experiences, this, too, is something scientists have only recently nailed down: a child's innate temperament shapes how the world treats him, with the result that that temperament is either reinforced or modified. A child who is innately shy, and who carries genes associated with shyness, can grow up to be as outgoing and socially adept as other kids if her parents encourage that rather than her introversion.

Killers who choose a high-profile crime like Cho's are reaching for one final chance to give their life meaning. "They may think, 'I may never amount to much, but I'm going to die amounting to something. This is my final mark on the world, my final statement'," says Jana Martin, a clinical psychologist in Long Beach, Calif. "[Their] fantasy is that they will have the ultimate last word, even if they don't live to see it." The video again: "You thought it was one pathetic boy's life you were extinguishing. Thanks to you, I die like Jesus Christ, to inspire generations of the weak and the defenseless people." Although that reeks of a messianic complex, there is very little research on whether religious belief makes it more likely that someone will resort to mass murder, or less. On a national scale, the countries of Western Europe that Pope Benedict laments are turning their backs on their Christian heritage have the world's lowest rates of homicide. At the individual level, there is some evidence that regular church attendance "promotes moral integration," says Jack Levin. But extreme religiosity to the point of hearing voices and seeing visions is often linked to schizophrenia.