Since the day serious quantities of testosterone started coursing through my body in adolescence, through its gradual decline in late middle age, I had regular dreams (a little MSG for dinner to make me sleep lightly, and I could murder half a village between sundown and sunset) and day-time fantasies that involved violence, mayhem, and personal physical triumph over various adversaries. Now, in my actions, I'm a pretty nonviolent guy. I don't carry a weapon; never hit anyone in anger, and have a strong tendency to prefer negotiation and compromise over winner-take-all confrontation.Not the kind of thing anyone's likely to bring up without internet anonymity, but yes, being a guy is like that sometimes. We're kinda nuts.
But, the seeds are there, and it takes a lot of socialization to sublimate them. I don't claim this to be a universal male phenomenon, but from what I know of my male friends, it's pretty close. Yet I've never talked to a woman who gets the faintest glimmer of recognition about this, unless it's related to a direct and immediate threat to her young children (in which case, many would swing a bat at an assailant's head without a second thought, as nearly as I can tell).
And, for what it's worth, this pretty much describes the state of the world for the domestic farm animals (although not dogs or cats), and most wild animals (but not all), I've encountered.
So - for 30+ years I carried this around in me. Thoroughly contained, but never absent. I'm not in the least surprised that enough stress or other mental illness breaks those barriers down in a few men, and that some of them, just go off at random once that happens.
(This argument has the neat trick advantage that, if a male reader says, "but I'm not like that at all," TBA can slowly shake its head and respond, "well, luckily for you, your testosterone levels must be relatively low ....")