The Columbine High School massacre was a school shooting that occurred on April 20, 1999, at Columbine High School in Columbine, an unincorporated area of Jefferson County in the American state of Colorado. In addition to the shootings, the complex and highly planned attack involved a fire bomb to divert firefighters, propane tanks converted to bombs placed in the cafeteria, 99 explosive devices, and carbombs. The perpetrators, senior students Eric Harris and Dylan Klebold, murdered 12 students and one teacher. They injured 21 additional people, and three more were injured while attempting to escape the school. The pair subsequently committed suicide.
Although their precise motives remain unclear, the personal journals of the perpetrators document that they wished their actions to rival the Oklahoma City bombing and other deadly incidents in the United States in the 1990s. The attack has been referred to by USA Today as a "suicidal attack [that was] planned as a grand—if badly implemented—terrorist bombing." The massacre has been reported as "the deadliest high school shooting in U.S. history."
The massacre sparked debate over gun control laws, high school cliques, subcultures, and bullying. It resulted in an increased emphasis on school security with zero tolerance policies, and a moral panic over goth culture, gun culture, social outcasts (even though the perpetrators were not outcasts), the use of pharmaceutical anti-depressants by teenagers, teenage Internet use, and violence in video games.