its a horrible situation and i seriously hope some good comes out of it and things improve so that it never can happen again

The ninnies who insisted on disarming the students, thinking idiotically that with a stroke of a pen, they magically prevent bad people from carrying guns for nefarious purposes, share some of the blame for setting up this situation.
attitudes like this really scare me i have to say - heres how i think your situation would go down

The Shooter walks down the hall shooting at his victims - a "hero" draws his gun and returns fire - someone further down the hall hears shots and see's the "hero" firing and so draws his gun and shoots the "hero" - the original shooter who was prepared and was wearing a Vest (as he was) would most likely survive and keep going - eventually you would get into the situation where students were shooting students for no other reason than they could hear shooting and were in a state of panic making the situation far worse

the solution isnt to arm everyone but is to arm NO-ONE including the original shooter - if guns are freely available then anyone could be carrying - its probably too late for this tho as the US has had freely available firearms for so long removing them now would be impossible


as to the cause i agree with an earlier poster its a fundamental break down of community that is causing this - we are having the same problem in the UK and it has a corresponding rise in violence