How to deal with someone else's anger?

So my BF has some anger problems ever since his accident, he will throw something or punch something. I've tried to talk him in to going back to therapy and he agreed he needs help but he hasn't gone...I terrifies me that one day if he doesn't get help it'll be me that his anger is taken out do I help him??? I'm not leaving him, because this level of anger doesn't happen very often but enough to worry me.