The Anatomy of Violence

Young killers tend to be highly suggestible, modeling their behavior on widely reported crimes. The Columbine shootings inspired several similar plans, and in Cho's video he refers to "martyrs like Eric and Dylan," the Columbine killers. The martyr reference is telling. In the most exhaustive study of school shooters, commissioned by the U.S. Department of Education and the Secret Service after Columbine, researchers examined 37 such cases involving 41 shooters over the previous 25 years. "By the time of the shootings, a good 78 percent of the perpetrators were suicidal," says Harvard University psychologist William Pollack of McLean Hospital. "Those who survived said they wished they'd been killed by the police. They were isolated, felt bullied, harassed. They want to die."

Still, feeling chronically frustrated, blaming others for your problems and being socially isolated are not sufficient to trigger a killing spree. "If everybody in that category were a mass murderer," says Peter Sheras, a clinical psychologist at the University of Virginia, "there would be no one left on the planet." To place the final blocks on the tower and make the whole thing come tragically crashing down, you also need the right environment.

Barely 24 hours after the Blacksburg murders, Australian Prime Minister John Howard lit into the "gun culture that is such a negative in the United States." That sentiment echoed across the globe and brought a reminder of how Kip Kinkel came to have such easy access to guns. "A psychotherapist actually suggested that his dad buy him a gun so they could have something to do together," says Loyola's Garbarino. "People in other cultures are blown away when they hear that."

Guns explain the high body count in Blacksburg and Columbine; you don't hear of many mass stabbings. But historians have long noted the American propensity toward violence independent of the ubiquity of guns. In his 1970 collection "American Violence: A Documentary History," Richard Hofstadter wrote of the "extraordinary frequency, [the] sheer commonplaceness" of violence in American history. Stanford historian Lawrence Friedman mused that it "must come from somewhere deep in the American personality ... The specific facts of American life made it what it is ... crime has been perhaps a part of the price of liberty."

By the numbers, the United States should have low levels of homicidal violence, which roughly tracks a country's income. Britain, for instance, had 1.5 homicides per 100,000 population between 1998 and 2000. Japan had 1.1, while South Africa had 54. The rate of violent death in the United States was 5.9 per 100,000—above even Turkey's 2.5. Clearly, culture matters. How?

The United States is a nation of immigrants. Those who choose to pull up stakes and try their luck in a distant land "have energy and are willing to take risks," says psychologist John Gartner of Johns Hopkins University. For most immigrants, that translates into a spark and drive that lead them to success in their adopted land. For a few, however, risk-taking coupled with impulsivity may set the stage for violence, Gartner says, "and you do see more violence in immigrant nations like Australia and America." If barriers of language or culture keep an immigrant child from fitting in, it can increase the risk that he will become alienated and, given enough triggers, resort to violence.