Like your opinion? (Venting)

Have you ever felt scared of your SO? Not him but what he might do? I know he will never hurt me but he has these dark, dark moments where he just wants to fight with someone. He wants to punch and kick someone to death. I know physically he could do it, but I also know he wouldn't. I just want to know how to help him through these moments. Without having to find bail money! (Joke to lighten the mood). How can I help a man who won't help himself.... And replies saying 'just leave him' aren't helpful.