Guns can't be controlled. How exactly would we do it? House to house searches, Iraq style? How many people would we be willing to put in prison for non-compliance? Does anyone think that Americans with guns are going to give them up because a law is passed? Are we willing for Prohibition III, the biggest and most futile of them all? What happens when fifty million or so people decide the law is wrong and resist -- some of them willing to fight? The tradition of owning weapons is seared into the culture. There is no way to oppose it without physical confrontation with the population of the U.S. Haven't we had enough stupid wars against our own people to "protect" them from some evil we believe they shouldn't embrace?
Coming soon will be homemade lasers, Faraday cannon, railguns... we can't stop people from having or making weapons. All we can do is make sure the penalties are high for using them.
As for the insane or the mentally sick, we will always have them. A lone kid can take out dozens with a sword if he's clever. Easy to make as well. They are successful because no one can anticipate madness at any moment -- no matter how many metal detectors, pat-downs, dog searches you throw at humans, a determined killer will always find a way. No one can anticipate every methodology. A new one will be invented as soon as one is deterred.
And we only think this is some new phenomenon because we can't do web or Lexis searches on the 19th century. You all don't seriously believe no farmboy went to school one day in 1845 and killed all his classmates? This has happened before and will again. What we really need to do is stop giving these psychopaths media coverage. THAT is the new factor in the would-be murderer's world - he knows that he will be on the news instantly, and be famous as long as a clip of file footage on YouTube or whatever exists. We've made them celebrities. We've given their psychoses grand scale.