If Greer heard the first shot, but wasn’t sure from which direction the shot came, it would’ve been natural, I think, for him panic and brake, fearing that he may he may have been driving right into a fusillade of gunfire. But that still leaves a question unanswered: If the frames showing the limousine nearly stopping were excised, why? Perhaps simply to cover their own asses? As an aside, I, too, think that the ‘theory’ of Greer turning to shoot Kennedy is implausible; It’s simply ludicrous, and only further muddies the water.