While this is common knowledge to most, this movie was inspired by the events of Columbine in 1999. Some scenes mimick the real-life massacre almost exactly. For instance, they planned to kill many more than they actually were able to because of the failure of their improvised explosive devices. The real killers had planned to murder at least 600 people, though it is not mentioned in this film the scope of the plan. Another, more obvious, link is the use of the Tec-9 assault pistol. One can also link the use of settings like the Library and the Cafeteria to the media coverage of the real event.
Link: http://en.wikipedia.org/wiki/Columbine_High_School_massacreFirearms.
