On April 20, 1999, the community of Littleton, Colorado, was shattered when a pair of teenagers launched a devastating shooting rampage at Columbine High School. At that point in time, the Columbine High School Massacre stood as the deadliest school shooting the United States had ever witnessed.
It all unfolded at 11:10 in the morning. Dylan Klebold, 17, and Eric Harris, 18, showed up at the school wearing trenchcoats and carrying two duffel bags packed with homemade propane bombs. They planted the bags in the school cafeteria, setting them to explode at 11:17 — but fortunately, neither device detonated. When it became clear at 11:19 that the bombs had failed, the two shifted to the second phase of their plan and opened fire on students. The shooting began outside the building before the pair moved indoors to the library, where the majority of their victims were found. By the time they turned their weapons on themselves, they had taken the lives of 12 students and 1 teacher while wounding 20 others.
With both shooters dead by their own hand and no written or recorded explanation left behind, a definitive motive was never established. Speculation spread rapidly — fingers were pointed at video games, music, the Goth subculture, and various other influences — yet none of these far-fetched theories were ever supported by evidence. What does seem likely is that retaliation for bullying played at least some role in driving the attack. In the aftermath, schools throughout the country responded by implementing zero-tolerance policies targeting threats of violence and disruptive student behavior.