I am going to coin a new acronym because I am getting tired of typing that there is not enough information to pass judgment.
NEI.
We do not see what led up to this point. The article does mention that while the man was still standing, he was punching at the officers. On the video, we can see several times the man kicking at officers who are approaching him (probably to turn him over and cuff him, but not, at that moment striking him nor making a move to do so). The man WAS resisting. I am sure the officers, in their horribly violent and stupid way, were trying to get the man to roll over so that they could cuff him. He is somewhat more dangerous to the officers while lying on his back than on his belly.
I am not justifying the officers' actions. At the very least, they need to learn how to handle a citizen who is resisting, but is clearly no real threat to their "safety." However, without seeing the whole video, including the surveillance camera, showing how we arrived at this point, it is impossible to say whether the man's rights were violated or what crimes (if any) the police committed.
BTW, the article says that the cellphone video is 5 minutes long and implies that they posted the whole thing. They didn't.
If folks want to make the case that these officers committed crimes and/or violated this man's rights, they should defend their position by finding and posting both videos in their entireties.
Until they do that, NEI.