Oswald did shoot JFK but it went further than that....Oswald was silenced by mob connected Jack Ruby before he could talk for some strange reason. Oswald was the money shot in the murder but doesn't mean he acted alone or was not a hit man for a controller. That was a tough shot with the rifle he used. Jack Ruby took him out on camera for the world to see. That's the signal that this wasn't a lone crazy man but a hired hit man.
And if that was the case, I think it caught him by surprise. I wouldn't be surprised if he never got a shot off or they would have had a bullet from that rifle as evidence.
Which could have been collected at any time prior... But it wouldn't look like that after 7 impacts. No way.