Well this was one of those serious fights that you have in any relationship, nothing new but I agree it must be a shock to you. My suggestion would be that try not to do stuff that triggers his anxiety or make him behave in an unpredictable way. I'm not saying that you must bear everything that he does but since you said he's dealing with bi-polar disorder I'd say you kinda have a responsibility for him. Not blaming you though. It's cuz it is a bit difficulty to deal with mental health issues and sometimes the action which seems to happen randomly makes the person vulnerable, it's not his fault either. I'd suggest to talk it out and make sure it never happens in future,good luck :)