I don't think he was in the car, I think he was HIT BY the car. If you look at the damage to the left front of the car, it matches up to the damage on the dude - right about where his legs were sheared off. Also, the fact that the windshield is caved in would indicate that his body went up and into it after impact.
Poor dude was really really skinny. Probably wandered into the road looking for a snack or something, and didn't see the car approaching.