you should never mix those two substances and if he is taking antidepressants in the first place he definately should not be drinking. this is probably a nasty side effect of the drink

I don’t think that the mixture is causing his behavior. I used to mix the two and I would usually just get terrible hangovers, so I would usually not take it much of it when I drank which was usually most of my waking hours. He is probably either an alcoholic or a potential alcoholic. I am a recovering alcoholic, myself, and I think that he is probably fueled by severe internal issues and alcohol.