Occasionally other people will get involved. I worked with a very nice man once but you wouldn't mess with him; he had a military background and was very open about the hard upbringing he'd had. He was a great guy, really sound, decent, straight up, friendly but not gossipy, fun and friendly but not flirty, committed to his wife etc. We worked in an industry that was rife with politics, money, affairs so he was refreshing.
Anyway one morning in the office he walked in looking uncharacteristically rattled. He said he'd punched someone on the tram and was expecting the police to arrive in. The team was mid chat and it was so bizarre it took a few minutes to get the details out of him, he was pacing looking very agitated. I'll call him Phil.
It went like this; the tram was absolutely rammed as it was at rush hour every morning. He was face to face with this woman when he realised she looked petrified and was shaking and crying silently. They locked eyes then she signalled to her left or right. He was totally confused as she didn't speak a word. He followed her gaze and he said he couldn't believe what he was seeing, a man had his hand up her skirt.
Phil said red rage descended on him, the tram had stopped and doors opened. Phil pushed forward and punched the man right in the face. He fell out the doors and onto the platform out cold and a crowd of chaos descended. Phil panicked walked through the throng of confusion and left, came straight to work.
He didn't know what to do, we calmed him down. We expected the police to arrive all day but nothing, no reports etc. He kept describing the woman's terrified face and each time he did you could hear the anger and upset in his voice. His eyes would widen as he described it, it was clear he couldn't believe what he was seeing.
I have to say I liked him even more after that.