We did Turner briefly in October after 'Professor' Norwood tried to use him as evidence of Jack Ruby going down the ramp, but, as you see, Turner has effectively ID-ed Bookhout, not Ruby. Did not recognize the face, he did recognize the hat, recognized Bookhout's heavy frame and, as a huge bonus, thought that the shooter was wearing an overcoat, or long coat. This reflected the fact that Bookhout was 5' 6" but wearing a jacket that seemed to go down rather farther than the ideal length for a person of that height.
So he arrived 3-4 seconds before the attack? I think that we can put this ramp matter to rest. Bookhout was hovering outside, waiting for a signal: in fact, he probably got three: a visual signal from outside or a window, a blast on a car horn and the car exiting the Main Street ramp with a maximum of fuss: making the TV people get out of the way, screeching its brakes and making the tires screech, on the ramp. He could also probably hear Petitt shouting: 'I want it! Give it to me!' Signal for the calm and level-heaved Bookhout to take the stage. He spent 3-4 seconds waiting beside reporters, lunged forward, fired the shot and, 3 seconds after the lunge, he had taken his dive into the swarm of cops. It was a 6-7 second appearance, backs to the cameras, and video later massaged.
Yes, I think that we have figured that one out.