Can a bouncer ault you off property?

My buddy broke a window next door to the bar we normally go to after closing time. We were waiting for our rides and he punched the window and shattered it. (Not the actual bar's window that we were at. It was a shoe store or something next door). Anyway, dumb thing to do. 5 bouncers immediately started running towards him so he took off running. Across the street from the bar they were holding him and tried to choke him out, but he got away and started running again. 5 blocks down the road my ride spotted him and he was covered in blood. The cops then pulled in to the parking lot that i found him in. The cops had the ambulance take him to the hospital and he needed 11 stitches over his eye. After he was hospitalized they took him to jail for criminal mischief and public intoxication. I guess my questions are...1. Can bouncers do anything to someone off their property?...2. What actions should my friend take?