There are 327 million people in this country. There's more than 1 gun per person, on average. Guns aren't hard to get.
If only 1 in 1 million is dangerously sociopathic, then there's 327 potential time-bombs out there just waiting to go off. Different sources claim sociopaths range between 1% and 20% (don't believe that last one) of the population, so with the best case there's more likely > 3 million sociopaths.
You can't remove the guns from the equation, Psy. It's been tried elsewhere, and didn't work. You can't put 3 million sociopaths in jail when they haven't DONE anything yet. Hell, we mostly don't know about the dangerous sociopaths until AFTER they've gone ballistic.
Look at the bright side: you have a helluva lot better chance of getting killed by a drunk driver. Every day, ~30 people in the US die in drunk-driving crashes. That beats the occasional shoot-em-up, hands down.