This was just uploaded to Youtube, and is just beginning to be mentioned on Twitter this evening. All I can tell you about the video is that the incident supposedly happened earlier Wednesday, and that as police attempt to arrest an occupier, he is pulled away from the officers and freed. "De-arrested" is what the occupier who posted the video calls it. Police seem to try to talk with the loudly protesting crowd of occupiers, but are met with chants of "Who do you serve? Who do you protect?" and "Show me what a police state looks like! This is what a police state looks like!"
The officers appear to be very unsure of how to handle the crowd - and perhaps a little afraid - and as the video runs out, they still don't seem to have a clue.
More on this if information becomes available.