Solange physically attacks Jay Z at the Met Gala

Beyoncé's lil sister physically attacked Jay Z in an elevator and even spat on him, while big sis Beyonce stood as an observer, doing nothing to mitigate the situation. This was all captured on surveillance cameras.

                                                 view video below....

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TMZ reports;

Jay Z was ferociously assaulted by Beyonce's sister Solange  ... who was wildly kicking and swinging at him inside an elevator ... and the attack was captured on surveillance video ... obtained by TMZ.

According to our sources, it all went down at a Met Gala after party last week at the Standard Hotel in NYC.  In the video ... Jay Z, Beyonce and Solange step into the elevator ... and then Solange goes crazy, screaming at Jay before unleashing a violent attack. A large man -- who appears to be a bodyguard -- attempts to hold Solange back, but she manages to connect at least 3 times.  At one point Solange throws a kick and Jay grabs her foot, but never attempts to strike her.  Beyonce stands by without getting physically involved. It's unclear what triggered the fight.

And this is interesting.  When you look closely, you see the bodyguard hit the emergency stop switch on the 12th floor -- mid fight -- presumably to keep the fight private.

All three walked out of the building together -- Solange looks pissed -- but while Bey and Solange get in one car ... security walks Jay to a different one.

see pictures of the trio leaving the building after the fight,  with Beyonce and Solange departing in one car and Jay Z in his own car.

                Solange can now add boxing/karate on her resume... hahahahah