During the Columbine High School massacre , Harris and Klebold planted two propane bombs in the school cafeteria . The plan was to kill as many students as possible in the explosions and to shoot down survivors when they attempt to flee . Both bombs failed to detonate , so the two students opened fire anyway , killing 12 students and 1 teacher , and injuring 21 others before both committing suicide . Another propane bomb was found south of the school , presumably as a diversionary device for the police . Other propane tanks were found in their cars , for use as car bombs
Columbine High School massacre
Columbine High School massacre
Propane bomb