I'm glad that we're looking at this from all angles, including the one where a guy whose job it was to fight and be tough suffers his own consequences in that. Those blows have an impact. Concussions will manifest themselves in all kinds of ways.
I imagine there's no on/off switch and firing yourself up on ice can carry over.
One of the reasons I felt empathy and protective regarding my ex was that he'd experienced some trauma and his fight or flight instinct was strong and ignited pretty quickly. Also, I've learned it was "comfortable" for me to live in turmoil. Normal.
It's important that all of this stuff is discussed and there's no stigma surrounding it. Looking beyond an incident to identify a root cause and perhaps changing the course of things for the future is important. Blame, shame...all the things that surround these incidents should be removed and the focus should be on fixing things.
With that, help is out there and there's really no excuse to explode and unleash on others and pass things along to them.
He's not a monster, but he's a guy with all kinds of resources at his disposal so it'll be up to him to use them if necessary. I hope he does.