Jamie wasn't entirely sure what the sound was - it was distorted by the other vehicles in the area. But that 'Ow' was pretty clear, and he's quick enough to put two and two together and figure out at least part of what is going on.

"Billy!"

He runs over towards the sound of the noise, just to make sure Billy's not too badly hurt. The rest of that sentence was pretty much gibberish, after all. Skidding to a halt by the very odd looking car, he asks worriedly, "Are ye okay?"