Police Officer Pushes Citizen Then Arrests Him

I am really confused by what happened in this video.  If you watch carefully, the guy that gets arrested didn't even move before the cop shoved him back.  To follow that, the other cop that wasn't even near the other two comes in for the arrest.  Now I have no doubt that the guys being questioned were probably being douche bags but the one that was arrested seemed to be complying with the office.  What do you think?