Of course he'll be canned -- he blew part of the coverup.
The one who actually killed Daniel will most likely get a promotion.
t-shirt: Just for info, there's no Columbine Police force. The over-200 who showed up at the school came from over a dozen different county and city agencies in the Denver metro area. That could explain some of the confusion.
My guess is that word went around immediately after the cop shot the boy, and all the silent brotherhood went into cover-up mode, and are still there.