I wouldn't be inclined to base judgement on the back of this snapshot of the situation.
There's no easy way to police mass demonstrations and I'm afraid that if the alleged victim and his brother had the inclination to be in the midst of mayhem then they were opening themselves up to such an occurrence. When things get this ugly, big-boys rules apply
This is why I have said that to encourage mass demonstration is irresponsible – things get out of control very easily.
I did notice near the end of that piece that a police officer was being dragged away from the immediate scene by some colleagues so there may some reason for concern, however, there's only a certain amount of shit that any individual can take before reacting inappropriately and police officers, despite all the training, are no different..
I've been in similar situations.