He had moved towards the car to record the license plate and then had baked off some. The cop then got out of his car and walked towards him...the guy wasn't really moving at that point and had moved back when the cop drew his weapon.
Also, that cop didn't act or look like he was the least bit worried about his safety. Usually when a cop draws his gun because he feels that he is in danger he will move back to get some space between himself and the suspect and get in to a defensive position, even if the weapon is still at the low ready. This guy just looked annoyed, drew his gun and then proceeded to stalk towards the guy over and over with his gun hanging down by his side.. That's an incredibly stupid tactic if you think the person has a weapon. That whole thing had "I'm pissed and now I'm going to show you that I am by trying to intimidated you with my gun" written all over it. I don't buy for a second that the cop was actually worried about the guy having a weapon. It was just an excuse, IMO.