They sure do, and if you ever saw a watermelon hit by rifle bullet, you see the pieces fall in front of where it was sitting. Physics dictate that the force of a bullet entering a body is focused in a small area so it punches through skin and into the flesh behind it. The exit wound is much larger because the force of the bullet is spread out over a much larger area, resulting in the object that was shot rebounding in the direction the bullet came from. Now, had the bullet stayed in Kennedy's skull, his head would have bounced forward, but since it exited, all that energy sprayed forward and, just like a rocket engine, caused his head to bounce back. Since it was attached to his neck, it had nowhere to go but straight back.
Seriously, what are they teaching kids in school today? Do they really believe that when a person gets shot, their body contents spray out of the entrance wound and not the exit? I guess since that's the way TV shows it, they believe it.