The Roseburg murders
As is often the case with mass murders, it will take some time to pin down the killer's motive. (I have my reasons for not using the names of mass murderers. See also Earth-Bound Misfit.) He was a student in the class where he committed the murders, and the teacher was among those killed, so there may have been some personal issue there. But it has also been reported that he specifically targeted Christians and described himself online as "not religious, but spiritual" and opposed to organized religion.
Knowing how the wingnutosphere has been blowing up a few cases of Christian business people being made to obey anti-discrimination laws into full-blown hysteria about "persecution", I can just imagine what they'll make of this once they get hold of it. So it's necessary to call attention to some basic points.
First, it seems unlikely that the killer had much in the way of a coherent ideology of any kind. He may well have been an atheist, but "not religious, but spiritual" is the kind of mealy-mouthed mush one commonly gets from people who have indeed abandoned religion (far from rare these days) but haven't given any serious thought to what that means or what words like "religious" or "spiritual" mean. He seems to have been one of those alienated, socially-isolated, angry loners who feel frustrated at how little impression they make on the people around them, and glom on to some charismatic and frightening ideology (it hardly matters which one, though this guy's choice -- Naziism -- is an obvious option) in the hopes that its glamour and intimidating qualities will rub off on them. Under different circumstances the same person might have become a KKK member, a Muslim extremist, even a militant Christian fundamentalist.
Second, we who have thought seriously about religion and fervently oppose it must take every opportunity to make it clear what that means. Christianity and Islam are the enemy -- but most individual Christians and Muslims are not. Yes, the violent extremists and those who seek to impose religious taboos on society by legislation are the enemy, but the great majority of people who call themselves Christian or Muslim are much more victims than villains. The explanatory metaphor of disease is a useful one here -- the fact that one opposes AIDS and wishes to see it eradicated does not mean that one has hatred or violent intentions towards people infected with AIDS. Quite the opposite. I do regard religions as mental parasites, harmful "memes" in the original Richard Dawkins sense, which have developed to infect human brains and alter behavior to help themselves spread from brain to brain. Yes, I hate Christianity and Islam, but I want to see their adherents cured, not killed. A murderous sociopath who acts in the name of hatred of religion is no different from, and no better than, any other murderous sociopath who acts in the name of anything else.
This guy is not evidence of a general atheist problem any more than the Charleston church murderer was evidence of a general white-people problem. They're both evidence of a general violent-sociopath problem.
Finally, I'm not oblivious to the fact that, as always seems to happen after mass murders like this, most of the blogosphere is once again making it about guns and gun control. I'm frankly too weary and nauseated with that whole argument to get into it again, but I'll reiterate a few painfully-obvious points.
While I have nothing against basic controls like background checks, it's absurd to think they could prevent attacks like this. They probably would prevent some impulsive murders and suicides, but in the case of premeditated mass killings, a determined person will always be able to get hold of a gun, no matter what the law is. If the government tried to ban most private gun ownership and disarm the general population, it would just do to guns what similar bans have done to drugs and prostitution -- drive them underground, out of reach of any regulation or supervision. Besides, in that scenario we would likely no longer be worrying about isolated mass shootings, because we'd be preoccupied with the all-out civil war which would engulf the country.
Countries like Israel which are serious about stopping mass killings at vulnerable places like schools require armed guards at such sites. The primary concern is terrorism, but armed guards would be equally effective at stopping a lone crank like the one in Roseburg. It's hard to see what else would be.
There are other countries where private ownership of guns is common but mass shootings are rare or nonexistent. Guns are not the problem and laws restricting them would have little impact on the problem. The problem lies in the sheer number and degree of aberration of those angry, hate-filled loners we're generating -- that is, it's basically a problem with American culture. See the higher rates of violence in red states and in conservative areas generally, relative to more liberal areas, despite the fact that (different local laws notwithstanding) anyone determined to get hold of guns can easily do so regardless of where in the country they are. See the high rates of violent crime in the 1980s vs. much lower rates today, though accessibility of guns hasn't changed. These variations represent cultural differences. That's where the roots of horrors like the one in Roseburg -- and the clues to what we can really do about them -- are to be found.