A good start …

David Brooks addresses the horrible Robert Bales mass killing here:
He rightly acknowledges that violent thoughts and actions “occur because we are descended from creatures who killed to thrive and survive. We’re natural-born killers and the real question is not what makes people kill but what prevents them from doing so.”
Brooks focuses on individual responsibility, what we might call personal evil …

Robert Bales, like all of us, is a mixture of virtue and depravity. His job is to struggle daily to strengthen the good and resist the evil, policing small transgressions to prevent larger ones. If he didn’t do that, and if he was swept up in a whirlwind, then even a formerly good man is capable of monstrous acts that shock the soul and sear the brain.

I think we also need to acknowledge the role of systemic forces – what we might call transpersonal evil. When, for example, an individual becomes part of a long-term occupying army, he is more liable to being swept up in a different kind of whirlwind, one that operates quietly and under the guise of patriotic propriety, like white privilege or entitlement or colonialism, setting up a power imbalance that leads to brain-searing atrocities. Michael Ware captures it here:

People may come to be seen as chattel, once you’ve stepped over enough body parts, picked up enough dying mates, and embraced that mind-set required to be purveyors of death in foreign lands. In that odiously dark place where our young men have to go in their heads to endure and survive and carry out the ugly deeds demanded of them in combat, these things must take their seat.

And Chris Hedges captures it here:
This is another cost of war … and another reason we should be deeply suspicious of those who are ready to march us down the path of war without counting the full cost.