This is the testimony of Bonnie Ray Williams, and it's important because he claimed to be on the 6th floor eating until close to the time of the shooting.
Remember that Oswald, supposedly, had to go to the 6th floor, set up the Sniper's Nest, retrieve his rifle, assemble his rifle, using a dime as a screwdriver (which they assume because they couldn't find any screwdriver) and generally get ready. Could he have done any of that with Williams up there? I think it would be impossible for Williams not to become aware of him. If he couldn't see him because of the stacks, he'd still hear him. And then he'd look to see who it was. So, I think we have to assume that for as long as Williams was there, there was no one there but him. So, what time did he leave? Well, in this interview, he estimated that it was 12:20 that he heard some commotion down on the 5th floor and figured that it was his friends, Jarman and Norman, so he went down there by elevator. And he was right, it was them. And he stayed there with them, and the three of them watched the motorcade from the window below the Sniper's Nest.
However, Joseph Ball challenged him about the time, and you can understand why. Joseph Ball wanted to give Oswald enough time to do what he had to do before the shooting, and the more time the better. I don't assume that 10 minutes would be enough. It sounds to me like Williams got there about Noon, and he ate his lunch which consisted of chicken on the bone (he kept referring to it as a chicken sandwich, even though there was no bread involved) some Fritos, and a Dr. Pepper. They found the remnants of his lunch. (I wish it had occurred to Oswald to urge the police to look for the remnants of his lunch in the 1st floor lunch room. That would have done a number on Frazier. But then again, if they had found it, they may not have admitted it. And whose to say they didn't look for it and find it and say nothing?) And remember also that there are two images of Williams at the 5th floor window during the motorcade. So, he was essentially telling the truth, and he had no reason not to. And of course, it is preposterous to bring Oswald into it at all. He ate his lunch in the 1st floor lunch room, and then he mozzied over to the entrance and wound up going out the glass door and standing on the top landing to watch the motorcade. But, there was definitely one man, and there may have been two or more up there on the 6th floor during the motorcade. So, what time did they get up there, and how did they get up there? Did they take the elevator? Did they take the stairs? And how did they get down? Again, stairs or elevator? And did they get to the 6th floor before Williams left? And then what? Did they just wait for him to leave? What if he didn't? Or did they arrive after he left? These are important questions for which we should seek answers.