We All Need to Vent

As I was driving home from work today I approached one of those large big family vans that have two or three rows of seats. From the left rearview mirror I could see the driver and I saw that he was shouting. Intrigued I drove a little faster to catch up to him, but by then he had stopped. But then out of the blue he started back up again. I drove a bit in front of him to see if there were any passengers, but if there were they had to be in the back seats because I could see none through his windshield. Then I slowed down a bit to let him catch back up. By now he had stopped again. But when he caught back up for a couple of seconds he started the shouting again. My windows were down but I couldn't make out anything he was saying. It all sounded like incoherent yelling. I also couldn't figure out what would be causing him to shout like that. He wasn't driving fast and wasn't stuck at a light so I don't think he was in any particular rush. I couldn't see anyone in the van with him. And the van, while it was a clunker, was getting him from A to B so it wasn't like he was shouting at the van as though he were trying to will it to drive on. I wonder if he has tourette's syndrome. I've never known someone to have it before, I've only seen that guy on youtube and it was sort of like that. This guy would just be sitting there driving along and then all of a sudden start shouting something unintelligible as hard as he could, all the while keeping his face looking straight ahead as though he were yelling at the window. Then he would stop again. It was a pretty amazing sight, but I felt really bad for him. Here it's a beautiful sunshine day and he's screaming bloody murder at seemingly random intervals. Something must have been really bugging him.