Should I report what I saw or mind my business?

Im a new yorker :-( and rush hour in the subway is nothing short over crowded. I was in the subway yesterday afternoon and there is a staircase leading down to the subway and an escalator that goes up but often times gettin to the escalator takes to much time so many people just walk up the stairs. There is sometimes a MTA employee directing the flow of traffic and trying to prevent people from walking up the stairs since it congests the traffic headed into the subway. In any case, he was trying to stop people and one gentleman continued walkin in which case 3 police officers intervened grabbing the gentleman by his shirt throwing him against a little metal barricade to arrest him. This obviously started the fiasco, he loudly questioned why he was being arrested and one of the officers screamed at him at least 2x to shut the F*** up. The young man exclaimed loudly that he was being arrested for walking up the stairs as he was drawing a crowd of onlookers. They started dragging him up the stairs and half way up one of the cops pushed him a little hard causing him to fall flat on his face while people were still trampling by. He screamed out again and the officer said again shut the F*** up. So they bring him upstairs and seat him on the bench and began askin him for id while he continues yelling that he's being arrested for walkin up the stairs. 2 more cops join the "fun" as they realize they are being watched and photos are being taken. In an effort to settle the situation they try and give him a ticket which he refuses so the continue with the arrest. Needless to say I have pictures of the incident and all of the arresting officers. Should i report them for their unneccessary use of force or should i just mind my business??