Columbine High School shootings, massacre that occurred on April 20, 1999, at Columbine High School in Littleton, Colorado, leaving 15 dead, including the two students responsible for the attack. It was one of the deadliest school shooting incidents in American history.

Three teenagers consoling each other at a vigil service in Denver to honour the victims of the shooting spree at Columbine High School, Littleton, Colorado, April 1999. Laura Rauch/AP

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The shootings were carried out by Eric Harris, age 18, and Dylan Klebold, age 17. On April 20, 1999, they entered Columbine High School in Jefferson county with semiautomatic rifles, pistols, and several explosives. In less than 20 minutes they killed 12 fellow students and a teacher and wounded 21 others. The violence came to an end when Harris and Klebold took their own lives. Officials later found two propane tank bombs in the cafeteria; had they detonated, the death toll would have been much higher.

News of the Columbine tragedy stunned the country. There was strong criticism of the slow police response. Despite the fact that the shooting ended by noon, police and sheriff’s deputies, believing there was continuing danger, did not move into the shooting area until several more hours had passed, during which time some victims bled to death. In the larger view, the Columbine massacre set off a national debate on how to end gun violence in schools, and a growing number of schools throughout the country invested in private security forces and metal detectors.

The official Jefferson County Sheriff’s Office account of the events included this moving coda:

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