[Uncle Chip]

The woman comes from the other side of the crowd — not the curb — in this video and appears to be taunting the cops and said something that upset the sergeant. When he turned in her direction she knew he was coming after her. It wasn’t the guy on the left of the camera throwing something that started it. It was something that she said that angered the police sergeant. That’s what it looks like.

[Ken H]

I see nothing of the kind. For the first couple of seconds, she's walking right past the cops and they don't even seem to notice her.

She and the cop then react at the same time to the water (or string?) that was tossed by the person in the black sleeves.