when the filming starts you see the driver reach to the left of his seat for the trunk release, he puts his friend in the trunk (the very 1st thing you hear is his friend saying "I'm not staying in for more than like 5 minutes.") and you see/hear the trunk lid close by movement you can see in the shot.
after he crashes his ride his friend uses the inside trunk release, jumps out and then grabs the camera, it's the kid (passenger) in the dark brown t-shirt we see running away w/the camera all helter skelter.......
The other purpose is to remind you that no matter what stupid things you do, there is always someone dumber than you. Much cheaper and better for you than anything Big Pharma has ever come up with.