This is what you see in the video.
First, as noted by others, the person filming the incident does a horrible job. Good portions of the video are simply footage of the grass and sidewalk at the feet of the operator of the cellphone camera.
When they bother to point the camera at the incident in question, you see a white, male cop essentially wrestling with a black, male detainee.
The footage (again, that we can see) basically shows the cop trying to wrestle the black male to the ground, pretty much unsuccessfully. It's three plus minutes of hand to hand combat. The cop makes at least one command to stop fighting him. Part way through the footage you hear what sounds like a taser being discharged (the narrator, whoever that is, seems to confirm this). You then hear multiple commands from the cop to the black male demanding that he let go of the taser, as they continue to wrestle.
The final footage shows the black male on his hands and knees, with the cop on the man's back, and the cop reaches to his holster to grab his gun, and fires.
I'm not certain anyone is going to jail for this incident.