What happens when a cop and a man who knows hits rights cross paths? It resembles a 3 year old throwing a temper tantrum. Except that this "3 year old" is 40, wears a badge and a uniform, and carries a gun.
Even if this guy was driving around and following this cop, it is totally his right to do so. Cops do it to us all the time.
Nicely done informed citizen, nicely done.