The police were slow to enter the school and were heavily criticized for not intervening during the shooting. But when several homemade bombs they planted in the school failed to detonate, the pair launched a shooting attack. Harris and Klebold, who planned for at least a year and hoped to have a large number of victims, intended for the attack to primarily be a bombing and only secondarily a shooting. Columbine still remains the deadliest mass shooting to occur in the U.S. history, until it was surpassed by the Parkland high school shooting in February 2018.
The Columbine massacre was the deadliest mass shooting at a high school in U.S. Another three people were injured trying to escape. Twenty-one additional people were injured by gunshots, and gunfire was also exchanged with the police. Ten of the twelve students killed were in the school library, where Harris and Klebold subsequently committed suicide. The perpetrators, twelfth-grade students Eric Harris and Dylan Klebold, murdered twelve students and one teacher. The Columbine High School massacre, commonly referred to as Columbine, was a school shooting and attempted bombing that occurred on April 20, 1999, at Columbine High School in Columbine, Colorado, United States.
