What are Jackie, G. Hickey, R. Willis and K. O'Donnell reacting to in Z-150?

[Tom Graves]

What are Jackie, Secret Service Agent George Hickey in the Secret Service follow-up car, JFK's guy, Kenny O'Donnell, in the Secret Service follow-up car, and "running girl" Rosemary Willis consciously reacting to in Z-150?

https://assassinationresearch.com/zfilm/z150.jpg

Answer: The sounds of Oswald's 1.4-seconds-earlier, missing-everything shot which he took half-a-second before Zapruder resumed filming at Z-133 (after a 17-second pause).

Also look at Z-60, in which Rosemary, no longer turned around, is now facing the camera but not looking at JFK and Jackie, but back towards the TSBD, instead.

https://assassinationresearch.com/zfilm/z160.jpg