This is a lengthy video btw. But everything seems to be going along fine, they arrest her, she is obviously drunk, and they put her into the back of the police car uneventfully.
But then this one cop (I am assuming a supervisor) shows up and pulls her out of the vehicle again, and starts it all off with twisting her arm, and then proceeds to slam her face into the police car and then slams her face into the ground. She literally shits herself in the video. She suffered a crushed orbital bone in her eye socket.
It was her house it turns out that she ran into while coming home. Her husband wouldn't even come out of the house when police arrived (indicates she may have problems).
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Link to video footage (unedited) and news coverage