A number of people over the years have said that the limo actually stops during this segment of the Nix film.
I have watched this GIF dozens of times, and what i see is the limo slow down to a crawl at the moment of the head shot, and then it starts to speed up again.
At Z313 (the headshot) SSA Hill has already jumped down onto Elm St & has taken a few steps & is level with the front wheel of Queen Mary (or praps just short of front wheel).
But the gif starts at about Z313.
During Hickey's accidental auto burst of at least 4 shots SSA Hill was hitting the tarmac & galloping to the wheel, hence he did not (he said) hear Hickey's shots.
