He just destroyed both of those cars and drove off!
That was just wrong, he knew exactly what was about to happen and did it anyway! This is some weird floating car bridge that is already flooded to begin with. We see two cars starting to cross, and they were being slow with it, so an impatient truck driver decided to pass them both. He caused the bridge to sink another couple of feet, and that flooded both cars. They were so badly under water that the one car was floating, and the truck just drove off like nothing happened!