On this date in 1999, two teenage losers looking for infamy (which I will not contribute to by naming them here) went on a shooting spree at Columbine High School in Colorado. The attack was originally planned to be a bombing using IEDs made from propane tanks. The killers planned to wait outside and shoot people fleeing after the bombs detonated, but the bombs failed to detonate due to faulty construction. At that point, the killers approached the school and began shooting people. They entered the school where they continued their shooting spree. They eventually committed suicide in the school library after police had surrounded the school. Twelve students and a teacher died in the attack. Twenty-four students were injured.
Wikipedia – Columbine High School massacre