There are a few technicalities that should be pointed out here though, to be fair about what we are seeing.
To start, we don't know why the suspect was being arrested. It's quite possible that it was a legal, even a justified arrest. Secondly, while we may see it as "brutality" to smack a suspect's head on the concrete, that is not necessarily true. A police officer does have the right to inflict pain in order to stimulate the cooperation of a resistant subject. In most departments, the amount of force which may be applied is relative to the amount of force with which the suspect is resisting. This practice is called the use-of-force-continuum. I am pretty sure that the pavement-head-crack is not a textbook maneuver taught at most police academies, on the other hand, gratuitous use of tasers and stun guns usually replaces such tactics in the modern era anyhow.
So what we are really left with here, is trying to gauge the level of resistance that suspect was giving police officers. This is difficult to accurately ascertain for two reasons. First, the video starts rolling just a second or two before the officer bangs the suspect's head onto the sidewalk. Secondly, we are not the officers affecting the arrest and therefore cannot feel the level of active resistance.
All in all though, my guess would be that the head-smack was more out of frustration on the part of the officer, rather than as progressive technique. I have seen on numerous occasions where an officer will believe that the subject is resisting, while at the same time trying to bend an arm a way it cannot bend, or when an arm is trapped under the subject's body while officers are piled on top bearing down with all their weight. So in many instances, what officers see as resistance, is really their own lack of understanding basic anatomy and physics.
Either way, my humble opinion is that the cracking of the head on the pavement was a bit excessive, and probably worthy of a reprimand, but does not rise to the level of many instances of brutality we have seen in other cases.
Next, we see the cameraman admonishing the police who arrive on motorbikes. for "invading our space." The police absolutely have the right to set up a perimeter and declare an exclusion zone in cases of emergency. This would include a reasonable amount of space around police officers conducting an arrest. This is not at all unreasonable, and done for the safety of both police and the suspect. I understand where the cameraman's anger comes from, but he is wrong. He does not have the right to interfere with the arrest.
Back on the other hand though, and again understanding where civilian anger against the police comes from, take a look at the security guard's face as he walks past the cameraman and back into the building. A sideways glare, a lick of the lips, and a frustrated grin. It's plainly written on his face that he would love to kick the ever-loving shit out of the guy holding the camera and carrying on with his rant against the police.
Okay, with all that said, and without further ado, here's the video: