The question is not whether they are both reacting. The question is what are they reacting to? According to all the evidence there was only one shot to that point.(z225-z240). And, according to the evidence JFK is reacting to it passing through his neck. JBC is reacting to hearing it, recognizing it as a rifle shot, and turning around to see if JFK was hit in what he feared was an assassination unfolding. Everyone who thinks JBC is reacting to his chest wound is ignoring or rejecting large bodies of consistent uncontradicted evidence.
Jerry Organ made the same points I was going to make.
You (Mason) say that during z-226 through z-232, Connally is not reacting to being wounded. He is reacting to hearing the shot that wounded JFK. Connally was really first wounded at a later point.
But how did Connally react to hearing this shot around z222?
1. By his "Soon to be shot" coat suddenly bulging forward for one frame, as seen in z-224.
2. By his "Soon to be shot" right shoulder" suddenly moving forward, as if it had been hit from behind, starting by z-226.
3. By jerking his "Soon to be shot" right wrist up high where we can see his hat, which was held in his right hand, starting at z-226, the same frame JFK starts to jerk both elbows upwards.
It is as if Connally was psychic and started moving the parts of his body that was soon to be hit. Even his coat was psychic.
There were multiple amazing coincidences, if this was just Connally reacting to hearing the shots, and not Connally reacting to being wounded in the right shoulder, chest area and right wrist.