After the cop 1st pushes him, does he grab what ever the cop is holding?

It kinda does. You can see things heating up in the background leading up to the flashpoint where someone in yellow to the left of the victim appears to be shouting and gesturing at bike cop before pushing at their bike. Yellow person gets pushed back but it changes the tone (previous bike cop and victim were standing calmly watching things together), bike cop pushes the victim back who then appears to make some very quick motion with his left hand towards bike cop. Bike cop interprets that motion as some kind of threat, starts pushing the guy but gets tangled on his bike and falls, creating this situation where they're pulling on the shirt of the victim to support themselves and therefore dragging the victim forward making it look like he was more involved than he actually was.

All of this happens in a couple of seconds, and it's a very tense situation so I can understand how maybe from a different angle people misinterpret actions as threats and things can escalate. This is exactly why you don't take this kind of approach to large scale protests, though. It creates unnecessary tension and puts everyone at risk.

Hey it’s not easy knowing all your convict forefathers would slit your throat rather than spit on you. Maybe the hats help.