Kennedy was shot twice: first through the neck (by the bullet that went on to pierce Connally), then in the head. The Zapruder film captured this shot too, in Frame 313. The image was deemed so horrifying that it was excised from public viewings of the film until 1975, when President Gerald Ford (who’d served on the Warren Commission) ordered it released. I remember watching the fully restored film on TV. It really was horrifying. You saw the top of President Kennedy’s head literally blown off. But it was creepy for another reason: the blown-off piece of his head blew backward. In other words, it looked like that fatal bullet was fired not from behind Kennedy, like the first bullet, but from in front of him. Were there two gunmen after all—Oswald in the book depository and someone else perched in the area known as the “grassy knoll”?
I went back to the library and scoured the Warren hearings. There I found neurologists testifying that a nerve ending can explode when hit by a bullet and that the two trajectories—where the bullet came from and which way the nerve fragments fly—are not necessarily related. Experiments from the 1940s, in which bullets were fired into the heads of live goats, revealed this fact. So, the evidence of Frame 313 was at least ambiguous; it said nothing, one way or the other, about the plausibility of a second-gunman theory.
However, in 1975, CBS News, which was doing a documentary on the assassination, hired a tech firm to conduct a high-resolution analysis of the Zapruder film, using instruments that hadn’t existed in the Warren Commission’s day. The firm discovered that, on Frame 312, Kennedy’s head slammed a tiny bit forward, and much more quickly than it jolted backward an instant later on Frame 313. The implication: The bullet hit his head from behind, pushing him forward, then a nerve exploded, which happened to push him backward.