Don't watch this video if you don't want to see an attack that results in bloodshed.
In this video, which may have been taken in Shanghai, a young man throws seed shells on the floor of a subway car in defiance of other passengers telling him to stop. Suddenly, a man in a costume runs up and violently attacks the litterbug with a rubber hammer, drawing blood. The attacker is accompanied by a woman in costume. Are they cosplayers or misguided real-life superheroes? It's hard to tell.