There were two entrances to the ramp: the Commerce Street entrance and the Main Street entrance. No doubt, Sam Pierce was there as a guard; to keep people out. That is, all people except for one person: Jack Ruby, whom he let in.
At the Commerce Street entrance, they parked the big Brinks truck right there in the driveway, effectively blocking off the entrance. You can see it in all the films.
So, they had both entrances blocked off, but one set up to allow one person, Jack Ruby, to walk in. The time was probably shortly after 11. Sam Pierce had a radio in his car, and he probably alerted someone that Ruby was on his way. When he got there, the fake procession commenced and Ruby was pounced upon and dragged away. Then, they quickly reconfigured the scene and started it again for the cameras, this time with James Bookhout filling in for Ruby. They took Ruby's gun from him, so they had it to give to Bookhout.
You notice as you watch it that it seems like a rehearsed wedding procession. Fritz comes out, and then and looks behind at the trio, and then proceeds to walk in a very formal, practiced manner as if he is enacting something.
Neither Leavelle, nor Oswald, nor Graves react to the shooter- or show any awareness of the shooter- until AFTER the shot is fired, although Oswald did visually acknowledge the shooter before he made his bolt. Oswald was like Paul Newman in The Sting except without scratching his nose.
It's the same look. They must have told Oswald that they were going to get him out of this, but they had to fake his death. Of course, they planned all along to double-cross him. Yet, I just don't believe that Bookhout actually shot him with a real bullet. I think it was faked just as they told him it would be faked. And because Oswald wasn't really shot, they couldn't let us see him afterwards. That's why we never saw Oswald being picked up and carried inside. Who knows, maybe they didn't pick him up at all. Maybe they just made sure that he was well covered, and then he just scurried inside. That would have been the fastest way to do it. Leavelle said that he and another cop picked Oswald up. But, that would have created a three person monster. How could the cameras have missed that? And wouldn't the cameramen have been hell-bent on capturing it? After a person has been shot, who is the most important figure? It's not the gunman; it's the victim. So, why didn't all the cameramen hone in on Oswald? Why didn't they position themselves to capture him? Doing whatever it took, running, pushing, shoving? How did it happen that pandemonium is all we saw, and why would any honest person be willing to accept that? You think they faked a bus and cab ride, but they didn't fake anything here?
The jail transfer was scheduled for 10 AM. It didn't happen until 11:20. Any idea why? I'll tell you why. They were waiting on Ruby. He was a bit late.