Victoria Adams spoke to detective James R. Leavelle of the DPD on 2/17/64. This is part of her statement: "When the President got in front of us I heard someone call him, and he turned. That is when I heard the first shot."
Suddenly and very rapidly jerking their heads around from right to the left and back again almost simultaneously is not normal. It’s an indication that something unexpected has happened. I believe that it was the first shot.
Again the difference between your approach and mine is verifiable photographic evidence.
It is not photographic evidence that differs. The photographic evidence has to fit well corroborated independent consistent witness accounts. It is our interpretation of the photographic evidence that differs.
The comment of Adam's is important. You will recall that as the President approached the Woodward group, he was not looking at the north side of Elm. So Mary Woodward yelled to him and she said he responded by turning and waving. Just after the President passed by the first horrible ear-shattering noise was heard. So Adams' statement fits with Mary Woodward's statement and a first shot just after JFK passed by Mary Woodward. That puts it after z190. The first shot.
I am not sure what you are looking at around z133 to think that a first shot occurred there. No witness says it had to be that early and dozens said it had to be about 60 frames later.