He's had training. Definitely a pro of some sort. Perhaps tactical police or special forces.
as for this guy having some sort of special training, I doubt it he just knew how to through a couple good punches and the 3 going after him didn't know how to handle a punch.
Then some big ass mother fucker came up and got in between them, then the cops showed up and this big ass mother fucker was crazy as hell... a cop put his hands on this guy and he fucking pushes the cop, looks at another cop and says "I could kill you in under a minute you stupid faggot, touch me again"...." Then he screams out "I was in the army bitch I've killed more people then you could imagine".
That was the only time in my life I've ever seen a couple cops back off of a guy and not try to take him down. They looked scared.
Real life hand-to-hand tactical maneuvers don't appear pretty or elaborate like in the movies or what you see at Karate boutiques. It's calculated force. Like Mike said, you can tell be his stance and how he calculated his punches, combined with the controlled manner that he backpeddled from the aggressors the entire time that he's definitely had tactical training.
I've seen guys like that. The taser teaches manners very quickly.
Electricity cares not about the size, strength, or experience of the individual.
I think that's Chuck Norris in disguise!