Beyonce's sister was caught on surveillance footage throwing punches and kicks at her brother-in-law, until security intervened.
Solange Knowles doesn't appear to be a fan of her brother-in-law.
The sister of Beyoncé launched herself at Jay Z while in an elevator just before exiting a Met Gala after-party.
The altercation occurred on May 5th and was caught on CCTV, which TMZ have obtained.
Solange can be seen clawing, punching and kicking the 44 year-old music mogul while her stunned sister can only look on.
The 27 year-old in-law was obviously very upset with Jay, as she attempted to attack him several times until a bodyguard stepped in to restrain her and appears to push the stop button inside the elevator.
This can only be presumed to hopefully stop their argument before entering the lobby at the Boom Boom Room at New York's Standard Hotel.
Even though Solange is held back by security, she still continues to verbally attack Jay but as the tape has no sound it is still unclear what triggered the attack, but she reportedly "overreacted" to a comment he made.
A source told Us Magazine, ''Solange flipped out over something Jay had said, that she took the wrong way. She took it too hard or too far. Not sure what it was, but she greatly overreacted.''
The 'Losing You' singer stormed out the elevator looking very agitated, while Beyoncé and Jay closely followed behind her.
The singing siblings were then spotted getting into a car together, whereas the '99 Problems' rapper chose to leave the venue separately in another vehicle.
Watch the CCTV footage below
Following the leak of the CCTV footage, the Standard Hotel released a statement promising to take action for a "clear breach of our security system."
"We are shocked and disappointed that there was a clear breach of our security system and the confidentiality that we count on providing our guests," the hotel's statement read. "We are investigating with the utmost urgency the circumstances surrounding the situation and, as is our customary practice, will discipline and prosecute the individuals involved to our fullest capacity."
Jay Z and Beyonce arriving at the Met Gala