Full disclosure. I'm a cop. I don't work the streets at the moment, but I have in the past.
I watched that video a couple of times and my conclusion is that it was staged. Look again around the 25 second mark when the "cop" is striking the suspect who is out of view of the camera. You can see the suspect's foot sticking up in the air and it appears the asp is striking the pavement between his legs. It also sounds that way, since you can hear the asp striking the pavement. An asp striking a human body doesn't make anywhere near enough sound to be recorded at that range and under those conditions.
Also, look towards the end of the video when the "cop" is escorting the suspect towards the gas station. I didn't see any sort of radio, microphone, or microphone cord anywhere on his person. No cop on the street is without a portable radio.
There are other clues too, but I won't belabor the point.
If it were a real assault perpetrated by a real police officer, I'd be calling for his criminal prosecution just the same as any sensible person. We're not above the law.