Oh oh, looks like we've got a potential shooter on our hands!
I think the history of the US which includes a long line of gun culture and availability, along with pressure to be popular. liked (this is by no means restricted to the US), computer games, violent movies, psychological issues, youtube fame, and so on and so on is the melting pot where all these issues come together to result in this outcome.
Guns are far too prevelant in many areas now to make gun control an issue. It's the same as the whole troop surge thing. You reach a tipping point where the only viable solution is to flood an area with strength to combat those who are abusing the strength they have, can buy over the counter.
Am I right to assume that some areas have greater gun crime than others? Would it be feasible to say that perhaps strict gun control in places like Boston or Connecticut and so on would be ok but the opposite would be needed in places like Michigan, Texas and so on? (sorry if my examples are out, but I don't come from the US and am not up on localised violence rates).