The common misconception of what you see in the Z film is shots were fired there. They were not. Kennedy is simply fluffing his hair, looking around, bringing his arm down and then getting ready to wave to the women to the right of him because they yelled out.
Go to film and photos of the parade and you see this movement of him throughout. I could post here a hair fluffing photo, a sequence where he does the same, he's waving then leaning on the car, and so on. But I won't - look it up. It's not hard to find.
We have to give the conspirators a little bit of credit. They knew the oak tree was in the line of fire early on Elm. They knew that if they started firing away too early, it would have blown everything. The kill zone is pretty much exactly where you see it in the Z film - right as he reappears from the sign. This video goes into detail about it.
https://drive.google.com/open?id=0B7Hr9Lrku-Cxa3NqTEpScWNQZncI simply have never understood why people think there's shots fired earlier, sparks flying from the curb and other nonsense. It's pretty straightforward - the vast majority of ear witnesses said they heard 2 close together shots and then the head shot. The Z film backs this up.
'Night John Boy. 'Night Mary Ellen.