Earlier quoted context omitted.
> because he's not like the rest of us. He's human and killing other humans is something a humans can do, given the right circumstances.
Yes, but normally you have a fairly high bar to cross before you would resort to such an act, and it would be in the context of self defense or something equivalent. To kill your wife in a premeditated manner is not something most humans can do, even given the 'right' circumstances, most people would resolve a conflict at that level in a different way.
From my recollection, his wife was sleeping with another man, or there was some conflict between the two that was related to another man who I _think_ was supposed to be a friend to them both.
it's been a while, but the point remains, he very well could have been in a state that allowed him to "pass that bar".