Why couldn't he just close that water tap himself?

In a scene after Sanya got bullied, our main "thief" character in that area confronts him while using the tap to wash himself and then tells him to close it and walks away, only to have the bereaved Sanya open the tap to the max and flood the area.

Why couldn't he just simply close the tap himself after using the sink and did it not occur to him perhaps that after being picked on and confronted by his younger co-residents in that area, and crying and loudly claiming he doesn't want to live here anymore, he might perhaps take out his small aggression on the tap and sink? And yet he just tells him to do it and then walks away, and then Sanya causes the flood and gets himself, his mom and Tolya into trouble as a result.

So why not just shut it yourself after use? Cheers.