Beyonce‘s younger sister Solange attacked Jay Z in the elevator after the Met Gala while they were headed back to their room at The Standard.

TMZ released black and white footage of the altercation and Solange and Jay Z can be seen entering the elevator then exchanging words before Solange started throwing punches. Before Beyonce’s bodyguard Julius could intervene, Solange landed a few hits on Jay. Beyonce then steps in front of Jay

What could have happened to make Solange angry enough to attack her brother-in-law Jay Z?