I read that we have 50 witnesses that saw the presidential limo stop before the fatal head shot. I watched Doug Horne's doc on the Zapruder film, which was very good and shows a strong case of alteration of the Zapruder film that would have taken those frames out among other changes. If you believe in those items as I do, how would have Greer known when to stop the limo? At a certain place, after hearing the first shot(which would be tough), a sign(Umbrella man, other), completely by accident, or other? I don't buy into Greer shooting Kennedy. Also if Greer is involved by stopping on purpose, isn't that a huge risk, hoping he is not shot in the process, putting faith in the gunmen not to miss?