For anyone asking why, Randy Brown sums it up best:
“Once you hate the bullies and no ones does anything to defend you, you hate the people in the class that don’t say anything, you hate the teacher that doesn’t say anything, you hate the counselors that allow it to happen. They, in essence, end up hating the school. Not just the bullies, they hate the school, and they want to kill the school.”
“During the shooting you can hear Dylan saying all kinds of things to people before he kills them, but Eric doesn’t. I mean there’s a very distinct difference between how the two handled the shooting that day. Eric is much more stoic. He does laugh about a few things, but Dylan’s having the time of his life, like it’s a party. And he’s killing people like he’s a party. It’s unbelievable how happy he is; he’s giddy about doing it.” - Brooks Brown about Eric & Dylan’s behavior during the massacre in the documentary The Columbine Killers, 2007.