Second Amendment thoughts

I have been reading some ideas from the second amendment debate. Those who favor gun control use the argument that if the framers had intended free use of guns by the citizenry regardless of participation in a militia, they would have left out the first part of the sentence and just stated that "the right of the people to bear arms shall not be infringed". But they didn't leave it out.
Opponents of gun control use legal precedent to bolster their argument that the courts have largely favored individual rights, starting with the Reconstruction when freed slaves were allowed to arm themselves against lethal Klan aims. They favor the right of law-abiding citizens to arm themselves for hunting and self defense.

To me, the problem comes down to this: what do we do about law-abiding citizens who buy arms and then become non-law-abiding? And what about non-law-abiding citizens who haven't been caught yet? I don't hear much debate on this question, which is buzzing along just beneath the surface. Just yesterday an employee in Henderson, KY blasted away at work, killed 5, then himself. Up until the moment of his action, he was law-abiding.

What do we do about him and his ilk? Do we treat him like a tornado or a lightning strike? Shrug, and say that there is no way to protect us against him? Or do we all start carrying concealed weapons, so that if he shows up at work or on the campus and pulls out his gun, there's a slim chance that one of us will plug him before he opens fire? Why is this dilemma so egregiously American? We don't read about this in Sweden or France or Germany (gang violence excepted). Why is it such an exclusively American phenomenon?

I'd love to have a dialogue on this.