Problem is you're talking in circles, I'm not sure if it's a language thing, but it's confusing.
Bottom line: There was only one person on the 6th Floor, Lee Oswald.
In fact the film footage from the motorcade shows that while the window was open, he hadn't set up to shoot until JFK's vehicle had reached the corner. He wasn't loitering, and while we don't know everything that he did, we do know he had to stack some boxes to rest his rifle upon.
The rifle would have been stashed somewhere safe so that none of his fellow employees could find it, and he would have had to unwrap it, and get into position. This would have been the contributing factor for the first shot missing the target.
We know it was Oswald because:
1. He was in the building.
2. It was his rifle, his fingerprints are STILL on it.
3.He was the only employee to flee the crime scene.
4. He murdered Officer Tippet, and attempted to kill a second DPD officer during his apprehension at the movie theater.
You can play the Introduction to Philosophy game of "Nobody can really know what happened" all you want, other CTers do it all the time, but the EVIDENCE points to Oswald as the lone shooter. 54 years of silly games have yet to change this fact.