i would have pinkmisted the shooter, absolutely.
i carry a glock 40 and a keltec 32, I have for over 9 years now. I've been punched once, shoved a few times, and threatened, but never pulled it or even made it known I was packing.
I believe that teachers should be able to carry a weapon. I worked in rough public schools when i was a teacher and yes, some of the kids were packing and I knew it. You never want to send a kid to the office when you know he had 2 gun charges the year before and he's wearing his blue n grays. It's a helpless position to be in.
IMO, the teachers at VT should have had the option to carry a fanny pack with a weapon and a panic alarm. The first time that kid reloaded, he would have been dropped. You wouldn't have had 60 dead. Or maybe he wouldn't have entered the classroom at all.