I witnessed that incident as well.
Seems like they sort of had an argument, and the girl was
complaining that the guy was always raising his voice at her and
stuff. Then the guy said that he had enough, and was tired of
always having to give in to her. The girl was threatening him with
something, not too sure what, but seems that she has a hold over
him.
At this point, the guy slapped her and went hysterical. He began
slapping himself for no reason. The girl after being slapped,
obviously began crying. That's when the drama escalates, and the
guy tries to drag her out to the toilet to silence her.