tOn April 20, 1999, just weeks before Harris and Klebold were both due to graduate, Brooks Brown, who was smoking a cigarette outside during lunch break, saw Harris arrive at school. Brown had severed his friendship with Harris a year earlier after Harris had thrown a chunk of ice at his car windshield; Brown reconciled with Harris just prior to the shooting. Brown approached Harris near his car and scolded him for skipping his morning classes, because Harris was always serious about schoolwork and being on time. Harris replied, "It doesn't matter anymore." Harris followed up a few seconds later, "Brooks, I like you now. Get out of here. Go home." Brown, who felt uneasy, quickly left the school grounds. At 11:19 am, he heard the first gunshots after he had walked some distance away from the school, and informed the police via a neighbor's cell phone.
By that time, Klebold had already arrived at the school in a separate car, and the two boys left two gym bags, each containing a 20-pound propane bomb, inside the cafeteria. Their original plans indicated that when these bombs detonated, Harris and Klebold would be camped out by their cars and shoot, stab and throw bombs at survivors of the initial explosion as they ran out of the school. At noon, this would be followed by bombs set up in the pair's cars detonating, killing first responders and other personnel. When these devices failed to detonate, Harris and Klebold launched a shooting attack against their classmates and teachers. It was the deadliest attack ever perpetrated at an American high school until the Stoneman Douglas High School shooting on February 14, 2018. Harris was responsible for eight of the thirteen confirmed deaths (Rachel Scott, Daniel Rohrbough, teacher Dave Sanders, Steve Curnow, Cassie Bernall, Isaiah Shoels, Kelly Fleming, and Daniel Mauser), while Klebold was responsible for the remaining five (Kyle Velasquez, Matthew Kechter, Lauren Townsend, John Tomlin, and Corey DePooter). There were 24 injured (21 of them by the shooters), most in critical condition.
