Eynon makes a good point in his first OP.
Does anyone here REALLY think that we can establish and enforce ANY laws that will PREVENT mass killings?
If not, then what do we do? Analyze the problem. I think everyone agrees that "normal" people don't kill other people in cold blood. Something has to be different about them. Something upstairs. Some kind of . . . mental imbalance.
We will never "solve" the mental health problem in our country. But, enhancing our ability to cope with mentally ill people will make these incidents few and far between.