If you need armed guards in schools then you've already failed. The US needs to fundamental overhaul of firearms regulations. Just look at the UK - we heavily regulate firearms and have very little gun crime. And guns are still legal here - in fact we have four shotguns (semi-automatic, side-by-side, pump-action and regular) and a rifle in our house, plus I used to be a member of the local gun club.
The US needs to get over its obsession with firearms. The last thing it should be doing is throwing more guns at the situation. And rather than blaming movies or video games it should blame the news and the US military policy of illegal and senseless drone strikes - now THAT would kick off a shit storm.