The Columbine massacre was planned for a year by two students who seemed inseparable.

History · Published 3 October 2026 Swipe more like this →

In short: Eric Harris and Dylan Klebold, two high school students, spent eleven months secretly building an arsenal before the 1999 Columbine High School massacre. While often remembered as social outcasts, they were active students who left behind journals and videos that continue to fuel debate over their true motives.

Eric Harris and Dylan Klebold met in middle school and became best friends, eventually attending Columbine High School together. By their junior year, they were described as nearly inseparable. While early reports labeled them as unpopular victims of bullying, many peers later noted they had active social lives and numerous friends. They were not members of the so-called Trenchcoat Mafia, a group they had little to no affiliation with, despite their preference for wearing black trench coats.

The pair began planning their attack by May 1998, nearly a year before the massacre. They amassed weapons and explosives, including pipe bombs and propane tank devices, while documenting their intentions in journals and video recordings. In January 1998, they were arrested for breaking into a van, which led to a diversion program. Despite this, they continued their preparations, even producing a video titled Hitmen for Hire for a class project, which depicted them as contract killers.

The FBI later described Harris as exhibiting psychopathic traits, while Klebold was characterized as an angry depressive. However, these conclusions remain debated as neither had been formally diagnosed with personality disorders. The exact motive for the attack remains inconclusive, with various factors like mental illness, bullying, and media influence cited by commentators. The massacre, which killed 13 students and one teacher, became a defining event that turned the school's name into a byword for mass shootings.

The duo's planning was meticulous, involving the illegal acquisition of firearms through straw purchases and the construction of various explosive devices. They intended for their writings and recordings to inspire followers, though much of this material was never released. Their actions on April 20, 1999, ended in their own suicides, leaving behind a legacy that has been cited by perpetrators of subsequent attacks, a phenomenon often referred to as the Columbine effect.

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