relationship problems

so my fiancés mom was diagnosed with cancer last july and passed away on dec 24th. (me and his mom never really got along so we weren’t close and her passing hasn’t really bothered me) since her passing he has been a real jerk and his narcissistic behaviors are coming back again. he constantly is real mean and say hurtful things to me that i didn’t think he could say. he quit his job and is never home anymore. he is gone as soon as he wakes up till about 9-10 at night. i am trying to be there for him and help him through his grieving but he won’t let me. it has gotten to the point of i can’t even say anything about anything or else he claims i am “b*tching”. it just really hurts because i love him to death and i know he is hurting but i don’t know how much more i can handle. he hasn’t gotten physical with me but he has punched steering wheel, walls, etc. so i am just worried what comes next. he constantly is saying he wishes he could just die and i am at a loss on what i need to do not only for myself but for him as well.