I don't think these shootings help with our reputation overseas with being the safest country in the world to visit. I went to school with someone who was a shooter in one of the big massacres, and he seemed perfectly normal when I knew him, so even mental state of mind isn't necessarily a sign that you can mitigate the problem by finding the people before the commit the crime. Someone may just snap one day.
I think drugs play a big part in these things, as they can totally change a person. But drugs are perhaps a bigger problem that maybe too big to fix. But if these drug users and crazies don't have the guns to access, the amount of problems they can cause is reduced.