
Note how Secret Service Agent George Hickey, having heard what he thought was a firecracker, leans far over and looks down at the pavement starting around Z-145, about one second after Oswald's first, missing-everything shot at hypothetical "Z-124," half-a-second before Zapruder resumed filming at Z-133.
Note how Secret Service Agent Jack Ready, on the passenger side running board, leans over to his right and turns his head around during the same time frame, and how Secret Service Agent Glen Bennett, below him, leans over far to his right, too. (He said he started looking at JFK after the firecracker-like sound and that he saw a bullet hit him in the back.)
JFK turns his head quickly to his left starting in Z-144 and then turns it back to his right and starts waving to Mary Woodward and her three journalism colleagues around Z-175.
Governor Connally, having heard the first shot and recognized it as such, first turns his head quickly to his left starting in Z-150, and then turns it far to his right, starting in Z-164, to catch a glimpse of JFK over his right shoulder. However, JBC can't "see" JFK in Z-180 (etc.) because he has turned his head far to his right, too, and has raised his arm to wave to Wooward and Co., thereby obscuring his face from JBC's view.