Cosplayer attacks man on subway for eating sunflower seeds

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.