My DP does this when he is very drunk. He has ruined family events because he needs a drink to be sociable and then I get the abuse. Family wedding abroad, and I was pregnant - was vile. Totally appalled at his behaviour next morning, friend's wedding, same thing, my own brother's wedding - same thing. Family party, we were coming back and he started making abusive comments about both my brothers. He is always repentant. (He couldn't work out why he was horrible about my brothers, who he says are lovely)
He gave up drinking for a while to try and deal with it.
When I had another family event coming up and told him he could not get drunk and abusive and ruin it for me. It was always my family things!!) He was appalled at how serious I was about it and realised he couldn't. He didn't that night. I am often on edge though and worry about if he will go back to being 'that drunk'.
He did. The most recent time was at a school event two years ago, drank too much to relax and be able to talk to people. He took a dislike to somebody we were with, muttering sarky comments, embarrassing himself. I defended the guy when we got home (his only fault was not knowing answer to questions at a quiz as he was not British and didn't know the answers) and he was ballistic and made as if to hit me but didn't. Has very contrite the next morning.
He does still drink, just very little, a couple of glasses of wine at home. Its still there though, rumbling below the surface. He know he needs counselling as I do as we are both unhappy. He has some deep seated issues which alcohol unleashes. I am a happy drunk, he is a horrible one.
His mum was an alcoholic and his sister is heading that way. My dad was an abusive drunk too. Pattern here huh 
I think counselling would help him OP, and you, him to work out what his anger is and you for why you are with him (I know I need to take my own advice
.)