A lot of this uncertainty could have been avoided if Officer Baker had "patted down" Oswald inside the lunchroom. Baker was searching the building for an active shooter. He see's a man walking away from him, and he then just lets the guy go because the guy works there? If Baker had found that Phony ID on Oswald, and you believe that Oswald acted alone, then everything ends right then. This includes the Tippit shooting.