My boyfriend beat up a guy who broke into our house while we weren't home (a former roommate from a couple months ago), was treating me very rude and sending me obscene text messages, and threatening us, wishing us to die in a car crash and me to kill myself and all these terrible things (all via text), and my boyfriend ran into him later than day and punched him a few times, made his mouth bleed, but nothing too severe...

Does anyone know what charges could occur? Anyone have any advice? We were thinking about going to the police station tomorrow and talking to them (they came to our house while we were gone earlier). Can he get arrested if we do that?
In my last sentence I mean "he" as in my boyfriend. And can we press charges for trespassing??