I understand that it's not politically possible to tell students to fight back. Someone's going to get hurt, and then there's beaucoup dinero in a lawsuit from the School Insurance Authority.
However, it's also pretty clear that playing docile isn't going to work, either. If a gunman comes on campus, everyone is left hoping that he goes and kills someone else in another room, and we'll deal with survivor's guilt later on--when at least we're alive to have such guilt.
If no one on campus is armed except the bad guy, the number of good choices to make drops to zero in a heartbeat. What should we do? Hold hands and sing Kumbayyah while some nut gets his jollies blowing people away? No.