If I am ever involved in a shooting scenario like this I'll be rushing the bastard with my knife. I don't care if I get shot, I still stab the **** if he's only as far away from me as the other side of a classroom.
This is not nerd rage, I've inherited epic levels of grit and orneriness from my father, and I'm probably dead either way. This way I die fighting, and maybe save the lives of a few of my peers, my death won't be meaningless. Five inches of steel should at least slow a shooter down enough that somebody else can completely incapacitate him.