JFK was gone before any gun was fired ..

the famous Zapruder footage - although doctored by the security agencies to make it look like the car did not stop ... does show continuous events within the car.
At 254 approximately 1 minute before any of the numerous gunshots Jackie Kennedy or her hologram wheels round and puts a white batwing vase directly into JFKs face.
At this he lurches forward and she then holds him upright - and perhaps already dead by some alien contraption takes the human lead projectiles to conceal that fact.

One of the men in the car meanwhile dons a red pilots mask - perhaps a communication device of alien build that is not usually on human frequencies.