Well, the people sitting right next to him in the car didn’t hear him fire a shot, so it’s pretty safe to rule that theory out.
It’s just another conspiracy theory. However there are many people more knowledgeable than I that cannot understand how two full metal jacketed bullets react differently coming from the same box. One bullet passing through the bones of two people and remaining intact while the other explodes after it hits the cranium. Hmm... two different bullets, two different shooters? I don’t know.