Rule No.1 in family is to never get into a fight with your sibling's significant other. It's messy and can almost never be fixed. So what set off Solange?

Beyonce, JAY Z and Solange attended a Met Gala after-party last week at the Standard Hotel in New York City and according to TMZ, things didn't end on a happy note.

The gossip site obtained surveillance footage of the three getting into an elevator just before Beyonce's sister began physically attacking Jay. There is no audio in the video but it is very apparent that Solange is yelling at her sister's husband before hitting him several times.

A large man pulls her off of Jay and tries to restrain her. She begins kicking in Jay's direction. At not point does he try to fight back however, you can see Beyonce standing next to her man not doing anything.

There has been no reason given as to why Solange did this. Reps for the three have yet to comment.