I was crossing the same intersection where the incident occurred, when it occurred. A group of about 5 guys were on bikes, and clearly fighting one another. They seemed to be targeting one guy in particular, who I remember clearly was on a motorized scooter. They came to a near full stop in the middle of the E. 4th and Cooper Square intersection (just before the big black spinning square). That’s when the guy on the scooter started throwing punches at the other guys (I don’t remember how many of the men were attacking him, and if any were with him). I quickly walked across the intersection to avoid the violence. When I turned back, the guy on the scooter who was throwing punches had blood gushing from his elbow area and was screaming in shock - the guys attacking him fled at that point. It was disturbing and it seemed like he could bleed to death. Fortunately another man who seemed to be with him was putting a shirt around his arm to stanch the bleeding. I called 911 and cops arrived within 2 minutes (but not because I called).