In the video of this incident you can see the guy stomping the cop, then backing off. As he backs off, right in front of the camera, a cop comes along and genlty pushes him off to the side. I've seen it 3 times and still can't figure out how the lost him when the cop had his hands on him!
I could not believe my eyes the first time I saw it! There were lots of cops there, surely enough that this one cope could have detained the suspect until they determined what was going on.