|Jämsä old church burning in Finland in 1925 (Photo credit: Wikipedia)|
Of course, this brings us to what should be a fairly obvious problem: atheism has no shared creed or ideology of any sort. That means that any examination of what our atheist killer believed would quickly become an examination of idiosyncratic personal beliefs that had nothing to do with atheism. Unless someone wanted to claim that an individual's lack of god belief motivated the act, we would be finished with atheism and on to other areas quickly.
On the other hand, I can imagine scenarios where anti-theism could be relevant to understanding someone's motivation for violent acts. I have come across at least a few atheists who claim to hate not only religious belief but religious believers. They are bigots because they insist that all religious people are awful simply because they are religious. I find them every bit as despicable as the religious believers who insist that all atheists are awful because we do not share their religious beliefs. While I would not assume that most of these atheists are violent, I would certainly consider their anti-theistic beliefs relevant if I was trying to understand a violent act one of them had committed (e.g., bombing churches). Of course, I understand that most atheists are not anti-theistic in this way and that anti-theism is not part of atheism.
I can also imagine scenarios where either left-wing or right-wing authoritarianism could be relevant in understanding someone's motivation for violent acts. I have observed authoritarian currents among some atheists. I find the willingness to trample others' rights to impose one's will on others to be a concerning development that I could imagine fueling violence in a small number of individuals at some point. Of course, I recognize that most atheists are not authoritarians and that authoritarianism is not part of atheism.
Polarization and tribalism come to mind as other factors likely to fuel violence. Carving up the world into "us" and "them" seems to be a common prerequisite for all sorts of violent behavior. Some atheists certainly contribute to polarization and are extremely tribalistic, and the same can be said for some religious believers. These factors are likely relevant and worthy of consideration in understanding violent acts committed by religious persons and atheists alike. But once again, neither are part of atheism.
If an atheist were to commit an act of violence that we were seeking to understand, I wouldn't expect the fact that this person was an atheist to tell us much that would be useful. On the other hand, knowing that this person was an anti-theist (especially one who held bigoted attitudes toward religious persons), an authoritarian, was highly polarized, and/or tribalistic might be relevant.