I’m a 21 F living in a college-student-densed area in California, USA. My roommate is a 25 M, and his girlfriend(19 F) newly just moved in with him without giving me notice. This didn’t bother me much, until my roommate started to yell at his girlfriend loudly nearly every day. His volume is so loud that I, in my own room across the living room, can hear him. Today, I heard him yelling at his girlfriend again, with multiple cursing words, and his girlfriend crying saying “I love you, but I never get to talk back to you” etc. I know my roommate has certified anger issues (he told me), but this should not be an excuse of his behaviors. He used to be constantly yelling on his phone before his girlfriend moving in, and he yelled at me once too, though he apologized after.
I have suspicions that my roommate is being abusive, even manipulative towards his girlfriend. Should I do anything under this circumstance?
TL;DR: My(21F) roommate(25M) might be abusive to his girlfriend(19F), includes constant yelling, what should I do?