It would be better to teach every American to fight back with everything you have when faced by a shooter. You cannot depend on police to do it for you. There will not be time. You must save your own life or lose it.
Winner!!
This is the answer and its so simple.
Fact: A single man, even with a gun, is no match for a crowd. A lone man can only look in one direction, he can only shoot in one direction and it's a fact it's darn near impossible to shoot with five people on top of you. As soon as the nut jobs of this world find out that if they go in some place to try to shoot innocent people they are going to immediately get attacked from every angle the shootings will stop completely. A lone gunman is the easiest mass murderer to stop yet we can't see the forrest for the trees. We have taught people to do exactly the wrong thing and that is to run, hide and wait to die.