Thank you for that. We see that Jack Kennedy is clearly hit and JC is looking forward, in no discomfort and still holding his hat in his right hand. That ties with the testimony of Nell and John Connally quite well when they said JC was hit two seconds after Kennedy.
I guess you didn't notice he is in the process of flipping his injured right arm upward, a motion he began at exactly the same frame JFK's arms started moving upward, frame Z226. The reacted at the same time because they were shot at the same time. Well, a couple milliseconds apart. Close enough.