Think about what usually happens almost on que when one of these mass shootings takes place...the Anti-gunners use the dead bodies to fuel their movement.
Anti-gunners are the group that have the most to gain from such acts.
Also note that the majority of such cases happen in a posted "Gun-free Zone" (besides the fact that the shooters while crazy aren't stupid) such zones are championed as the ultimate "cure" for the "sickness" and thus more of the same can continue to happen,a snowball effect if you will.
Even though it can be shown time and time again that the reason these places were picked is due to the "Gun-Free Zone" status.
That is why no matter how many times pro-gunners bring up the issue of the "G.F.Z's" not working,Anti's plug their ears,or ignore what is typed and go on about why "G.F.Z's" other other restrictive rules are the best answer.
The only other reason I can think of is that the Anti-gunners are really that stupid.