[UPDATE BELOW] The annual Met Ball is among the hyper-classiest affairs in the city, but the real fun doesn't start until celebrities sashay off the red carpet and into the most exclusive clubs in town: The after-party elevators.

Solange Knowles probably thought she was safe from prying lenses of the paparazzi when she attacked Jay Z in the Standard elevator following last week's fete, but she was wrong. TMZ acquired footage of the singer, forever doomed to be known as "Beyonce's sister," in the act of trying to disembowel the rapper with her stiletto'd foot. Beyonce appears to stand by at ease as the assault plays out. Is she used to it by now?

TMZ commenters have begun analyzing the attack in earnest:

We need to be asking ourselves why Beyoncé looked at her in the way she did walking out. She is covering for something. This is not a argument but a lot of hostility that appears to have mounted up. You need to check in to reality if you thing JAYZ is as pure as the driven snow. Beyoncé looks a lot like a Whitney Houston lately and that makes me sick. Her performance and appearance is changing. Money doesn't buy honesty and loyalty. Perhaps her sister knows what Beyoncé is suffering from. Maybe she knows too much. Jayz looks just like all passive aggressive men do. I really would like to know what they are fighting about before we judge this woman's misery.

This is way better than the scene in the Met elevator.

Update, 3:04 p.m.: TMZ has released the video's extended cut, featuring 3:32 minutes of elevator action. (Solange takes a breather, but does fly at Jay with renewed rage just as the elevator doors open.)

What the hell happened!? A source told US Weekly that "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 Standard has also released a statement to the Grio, threatening to prosecute whatever party is responsible for the leaked video: "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. 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."