I don't have much to say about what happened this weekend other than the obvious: it's a tragedy, and I hope we are making adequate provision to care for victims who may now face decades of disability. But as to the rest--we still don't know why he did it. Many of the people who rushed to blame this on their political opponents made themselves look like first class jerks, an impression that was not improved when we got more information, and they doubled down rather than simply admit that they had perhaps jumped to conclusions.
At this writing, it seems as though the violent rhetoric this guy was listening to came from the voices in his head, not the radio or cable TV. There is no evidence that his ideas were significantly influenced by anyone, left or right, or that saying mean things about Giffords made his fixations worse; we're talking about someone whose main grievance seems to have been that she wouldn't address his concerns about a conspiracy to control the grammar of American Standard English.
This never looked much like an assassination, which usually targets a single politician, not nine-year-old girls who happen to be standing near them. And after reading his ramblings, it's pretty clear that he was some kind of crazy, and that his community turned away from his craziness rather than trying to intervene. But even that judgement may be premature. And anyway, it's not enough to say that he was crazy--even paranoid schizophrenia does not elevate the risk of violent behavior by that much. Most mentally ill people do not attack other people.
I'm not sure why it is so necessary that we identify a culprit in all of this. What good does it do us to know that he is, say, a paranoid schizophrenic? It may matter in his sentencing, of course. But it's far from clear that this knowledge would let us do what we want, which is to prevent this sort of thing from happening again. We are not going to prophylactically lock people up, and there is no "seems a little, well, off" list to which we can add people we don't want to have guns. Even extended magazine bans wouldn't have done much good, as he was carrying lots of spares. As I understand it, he was essentially stopped because one of his spare magazines malfunctioned, something which may be more likely to happen on larger capacity magazines. Anyone who practices a little can swap magazines faster than others can notice and decide to tackle them.
Blame is a way of simulating control: if we can just identify who was at fault, we can stop it. The problem is, when we can't identify any very plausible target, we too readily go after implausible ones: Freemasons poisoning the wells, or Federal Reserve bankers plotting to monetize the national debt. At worst, this tendency is dangerous, corrosive; at best, it leads us to make unproductive policy choices.
A terrible thing happened. We live in a universe in which terrible things happen. That's no one's fault--or maybe, everyone's fault. Either way, I don't see much in the way of solutions coming out of this--only terrible, terrible sadness.