in the beginning the guy on the ground seems to be grabbing the officer's hand, could have been biting it. Still, did seem excessive. But maybe he was hitting him more 'cos if the officer tried to get him cuffed gain the guy would bite his hand again.
I know for example that bouncers have to deal with all sorts of things, like somebody grabbing their nuts and squeezing..
you also don't know what the guy was doing.. He may have hit the officer beforehand And was pushed onto the floor. And he was probably arrested for drugs or worse.
You rarely see "police brutality" on decent people!
And it was clearly cut, they cut the beginning. or if video started in the middle, there was no introduction of what the beginning was.