I watched this video last night. Here's my take.
I see a cop frustrated that he can't get any cooperation from these kids. I can see that escalating things. Probably something in police procedure about it. I'll agree he was all over the place, but some people are like that. There was this guy who worked at McDonalds back in the day who was the fastest moving person I've ever seen. Everything he did was instant. I'd order a fry, an he'd have them scooped, in the fry bag and on my tray in 2 seconds. I thought he was nuts to take his job that seriously.
The cop's "barrelroll" was a trip. He literally tripped. It wasn't him fooling around. Rolling after you fall or trip comes from combat training. The kid on the video who witnessed it thought the same and mentioned it to his friend.
Anyone who says the guy that rushed him, causing him to draw his weapon, was a child or a "boy", or even a "teen", is delusional. That man was at least 20 and had plenty of mass to be a threat to the cop. He got shoved by his friend a little closer than I think he meant to get, but from the cop's perspective, his reaction to draw his weapon seemed warranted to me. The other two cops appeared immediately and chased down the aggressor, and he came back with a bloody mouth.
The girl part was sad. I feel for her. I don't know what exactly she said to him or did, other than not leaving when he told the group she was in to disperse, to get a reaction like that, but she wasn't cooperating with any of his commands. Once you're set on arresting her, for whatever she did, what could he have done differently? Sat her down, called her sweetie, and talked her into putting the cuffs on herself? He told her to get down, she refused. Force is necessary. Pretty sure that's by the book.
From the sounds of what happened (Twitter invite), this doesn't sound like an isolated incident. The incident of the kids showing up and crashing parties. Is this the first run in with these kids this officer has had? I'd be pissed too if every week it was these same kids running amuck.