High schoolers on alert

On April 20, 1999, high school senior students Eric Harris and Dylan Klebold murdered 13 students and one teacher in a school shooting and attempted bombing at Columbine High School in Columbine, Colorado, United States. Twenty people were injured by the gunfire, and three others were injured while trying to escape. The attack ended when Harris and Klebold committed suicide. The Columbine massacre was the deadliest mass shooting at a K–12 school in U.S. history until the Sandy Hook Elementary School shooting in December 2012. It was also the deadliest high school shooting until Parkland high school in 2018. Columbine is considered among the most infamous massacres in the United States, which as of June 2025, had inspired more than 70 copycat crimes, a phenomenon dubbed the Columbine effect, and Columbine has become a byword for modern school shootings. Harris and Klebold, who planned for roughly a year, intended the attack to be primarily a bombing and only secondarily a shooting. The pair launched a shooting attack after the homemade bombs they planted in the school failed to detonate. Their motive remains uncertain. The police were slow to enter the school and were strongly criticized for not intervening during the shooting. The incident resulted in the introduction of the immediate action rapid deployment (IARD) tactic, which is used in active-shooter situations, and an increased emphasis on school security with zero-tolerance policies. The violence sparked debates over American gun culture and gun control laws, high school cliques, subcultures (e.g. goths), outcasts, and school bullying, as well as teenage use of pharmaceutical antidepressants, the Internet, and violence in video games and film. Many makeshift memorials were created after the massacre, including ones using victim Rachel Scott's car and John Tomlin's truck. Fifteen crosses for the victims and the shooters were erected on top of a hill in Clement Park. Many people objected to the inclusion of crosses for the perpetrators and these were later removed from the site. Planning for a permanent memorial began in June 1999. The resulting Columbine Memorial opened to the public in September 2007.