I let off the gas and let him do his thing. Once he was 2 cars in front of me, I saw him speed around the back left of a tractor trailer, only to then jump right in front of the truck. When I say right in front, I mean he could have touched the front grill. He was in the driver's blindspot for the next 10 seconds before pulling far enough ahead. And yes, he is extremely stupid.
After finally closing my agaped mouth, he was already at least 1/2-mile ahead, but karma was about to get him. No, not in the sweet form of a ticket, but rather, it seems his backpack came flying off during his ride. I can't confirm it was on his back before, but I'm 70% sure he had one on while making his daredevil moves. Plus, I doubt someone's backpack would have made it out of a car in the 1 minute between his passing me and the backpack's arrival. It was still rolling back when I swerved to avoid it and after realizing it hadn't caused any accidents, I laughed knowing his unsafe maneuvers got balanced out in the yin-yang karma driving universe.