The Columbine High School massacre was a school shooting that occurred on April 20, 1999, at Columbine High School in Columbine, Colorado, an unincorporated area of Jefferson County in the 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 bombs rigged in cars. The perpetrators, two senior students Eric Harris and Dylan Klebold, murdered a total of 12 students and one teacher. They injured 21 additional people, with three others being injured while attempting to escape the school.