The folks at I-Monk have it nailed as far as the responce to Friday morning's tragedy; wordless tears a la Job's friends. Not quiet tears, mind you, for wailing out is proper, but this isn't the time for argument.
We get the stock argments from the left on gun control, stock arguments from the right on how no-gun zones at schools give shooters free reign until the cops get there and vague discussions on how disturbed folks shouldn't have access to guns from across the spectrum.
None of the three are likely to happen; the First Amendment takes care of the first, while gut resposonce from swing voters will nix the second. The logistics of idenitifying and disarming every troubled person will get nixed from multiple angles; the gun folks won't like it, the advocates for the mentally ill won't like it and the psych profession gets stuck with the prospect of having one of their charges going postal and getting hit with a malpractice suit for not saying something.
The nature of the American beast means that we have one of these every so often, and we really can't do too much about it short of turning into either the Wild West were a plurality of folks are packing heat or a police state where the mentally defective are locked up as a precautionary measure.
Some things just happen and we can't do much about them.