The Columbine High School massacre was a school shooting and attempted bombing that occurred on April 20, 1999, at Columbine High School in Columbine, Colorado, United States. The perpetrators, twelfth grade students Eric Harris and Dylan Klebold, murdered 12 students and one teacher. Ten students were killed in the school library, where the pair subsequently committed suicide. Twenty-one additional people were injured by gunshots, and gunfire was also exchanged with the police. Another three people were injured trying to escape. At the time, it was the deadliest high school shooting in U.S. history. The crime has inspired several copycats, including many deadlier shootings across the world, and "Columbine" has become a byword for school shootings.
In addition to the shootings, the attack involved several homemade bombs. Two of these were placed in the cafeteria, powerful enough to kill or seriously injure all people within the area, although they failed to detonate. Their cars in the parking lots were made into bombs which also failed to detonate, and at another location away from the school, two bombs were set up as diversions, only one of which partially detonated.