Sorry couldn't let this one go:
I hope you've internalized completely that it wasn't your fault - and you where just a kid trying to survive - again not your fault.
When the Littleton shooting hit the news this was the first thing on my mind. Lots of us know those events have deep roots in the local community.
You were a kid in an impossible situation; you weren't and aren't the responsible party. Most adults couldn't handle that situation, and the adults there didn't handle it at all. Your story and your roommate's story are just heartbreaking to hear. It makes me angry at the adults and, though I try to remember that they are conditioned the same experiences, at the attackers.