COLUMBINE, Colo. — Today marks 21 years since two students shot and killed 12 classmates and one teacher and injured 20 more before taking their own lives at Columbine High School in Colorado.
They were teenagers who were fans of Adolf Hitler, spoke German to each other and called themselves the Trenchcoat Mafia.
On Hitler's Birthday, Apr. 20, 1999, 18-year-old Eric Harris and 17-year-old Dylan Klebold went into their school and opened fire on students and staff.
At the time, the Columbine massacre became the deadliest school shooting in US history.
Most of the students who died were in the library of the school.
In addition to the shootings, the attack involved several homemade bombs.
Two of these were placed in the cafeteria, powerful enough to kill or seriously injure all people within the area, although they failed to detonate.
According to officials, Harris and Klebold had planned the attack for over a year and had written out the details in journals.
![](https://media.tegna-media.com/assets/KFSM/images/c555f231-8e6e-4f08-b020-303cc78e35de/c555f231-8e6e-4f08-b020-303cc78e35de_16x9.jpg)
![](https://media.tegna-media.com/assets/KFSM/images/c555f231-8e6e-4f08-b020-303cc78e35de/c555f231-8e6e-4f08-b020-303cc78e35de_1140x641.jpg)