7) Dealy Plaza, like most urban centers, is an echo chamber (an episode of Monk: The Defective Detective showed this quite clearly). So, the farther away from the shot source, and the more off the line of fire, the more likely people would be confused to the number of shots fired. The three ear witnesses below the nest--no confusion. Three shots. Those in the presidential convertible-three shots. Back to the Zapruder film and computer reconstruction. The first shot (pre-loaded) complete miss. That's the one Governor Connally looks around for--and JFK seems to react also. A second and a half later the car was clear of the oak tree and the second shot drills through JFK's neck and nails Connally in the back, exits his chest, and lodges in his right forearm. It takes about a half second for JFK's and the Connally's physiological reactions to being shot to show. The reconstruction shows the pretty strait alignment of neck, back-chest, and forearm from a downward diagonal angle--the sixth story sniper nest is the ONLY option--and that alignment occurs a half-second before the shot-reactions occur. QED. A second later, the kill shot. LHO realizes he's done it (looking through his telescopic scope, the result would have been unmistakable), and bugs out while the presidential convertible peels off.