Bump. I don't really have any movies I want to see but haven't, so I'll suggest Zero Day.
Andre Kriegman (based on Eric Harris) and Calvin Gabriel (based on Dylan Klebold) announce their intention to attack their school, Iroquois High School[3], ...
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Pretty good movie, it doesn't really glorify their actions, nor does it paint them as completely insane. Their "plan" almost seems like your typical teenage bullshit that you'd talk about but never actually commit to, right up until the end.
I like that both main characters seem to live happy lives, have friends or family that they care about, but still feel driven to commit a shooting that they see as "necessary."
(It's on youtube, but I can't find the full version there anymore. It only cut out the pipebomb scene, as far as I know. If youtube is easier, you really aren't missing much)