Before killer Bill Greer shot jfk, he braked the limo to an almost complete stop. Notice the motorcycles and follow-up car come to complete stops.
1) Houston Chronicle Reporter Bo Byers (rode in White House Press Bus)---twice stated that the Presidential Limousine "almost came to a stop, a dead stop"; in fact, he has had nightmares about this. [C-SPAN, 11/20/93, "Journalists Remember The Kennedy Assassination"; see also the 1/94 "Fourth Decade": article by Sheldon Inkol];
2) ABC Reporter Bob Clark (rode in the National Press Pool Car)---Reported on the air that the limousine stopped on Elm Street during the shooting [WFAA/ ABC, 11/22/63];
3) UPI White House Reporter Merriman Smith (rode in the same car as Clark, above)---"The President's car, possibly as much as 150 or 200 yards ahead, seemed to falter briefly" [UPI story, 11/23/63, as reported in "Four Days", UPI, p. 32];
4) DPD motorcycle officer James W. Courson (one of two mid-motorcade motorcycles)--"The limousine came to a stop and Mrs. Kennedy was on the back. I noticed that as I came around the corner at Elm. Then the Secret Service agent [Clint Hill] helped push her back into the car, and the motorcade took off at a high rate of speed." ["No More Silence" by Larry Sneed (1998), p. 129];
5) DPD motorcycle officer Bobby Joe Dale (one of two rear mid-motorcade motorcycles)---"After the shots were fired, the whole motorcade came to a stop. I stood and looked through the plaza, noticed there was commotion, and saw people running around his [JFK's] car. It started to move, then it slowed again; that's when I saw Mrs. Kennedy coming back on the trunk and another guy [Clint Hill] pushing her back into the car." ["No More Silence" by Larry Sneed (1998), p. 134];
6) Clemon Earl Johnson---"You could see it [the limo] speed up and then stop, then speed up, and you could see it stop while they [sic; Clint Hill] threw Mrs. Kennedy back up in the car. Then they just left out of there like a bat of the eye and were just gone." ["No More Silence" by Larry Sneed (1998), p. 80];
Greer pressed on the brakes in the Muchmore film. The brake light illuminates.