I do not know the source of this image, but that's Umbrella Man. Some people think he was the one shooting the frozen darts, but I doubt it. I think he was just a signaler. But, what I want you to notice is how blurry the limo is.
Why is it so blurry, and why do you accept the blurriness? It's so blurry because they made it blurry because they don't want you to see what it shows. And what it shows is JFK reacting to having been shot in the back. But, they really went overboard with the blurriness here because it is just preposterously blurry. They really turned it into noise. And that suggests how revealing it must have been, with JFK showing that "quizzical look" that Jackie spoke of in her testimony.