John,
I am not disagreeing with Lee's basic premise, I just don't understand what he is saying about the direction of the shots and evidence of bullet and bullet fragments and the damage they caused to the vehicle.
"Couldn't a bullet from the back have an equal chance of penetrating the windscreen?"
Yes, it is possible. A bullet or larger bullet fragment traveling from the rear toward the front of the limousine could penetrate the windshield. Not sure how this proves more than one shooter.