Their work was supported by the National Institute of Justice. The first lesson taught by assassins is to discard stereotypes. Killers are not necessarily mentally ill, or socially isolated, or even male. Their second lesson is not to expect a threat. A threat would keep them from succeeding.
Few assassins express hatred for their victims, easily shifting from one target to another.
Harris, the son of a career military man, kept a diary of his plans for a year. The week before his suicidal attack, he was rejected by the Marine Corps. Most assassins behave in ways that concern the people who know them. Despite another student's complaint that Harris was making threats on his Web site and testing pipe bombs with Klebold, sheriff's deputies did not interview either student, or talk with their parents, or examine the Web site. John Kiekbusch of the Sheriff's Department of Jefferson County, which includes Columbine.