Men masturbating to women in public..

On trains or public places etc 😷😷😷.

I read an article that spoke about some crazy guy doing this in the train station near me. So I googled it to see if this actually happens and I read so many stories about it its crazy some people even said the strange men would ejaculate on them in their hair 😷💩💩 and nobody would say anything. Would you say something if you saw this? I feel like ide be afraid that the person who clearly isn't normal could be dangerous but part of me feels like it's not right to just stay silent in such a situation not sure what ide do 😔.