I'm saying that your claim "according to Jackson . . . someone was sticking a rifle out the sniper's nest window" is false.
Mr. JACKSON - Right here approximately. And as we heard the first shot, I believe it was Tom Dillard from the Dallas News who made some remark as to that sounding like a firecracker, and it could have been somebody else who said that. But someone else did speak up and make that comment and before he actually (finished?) the sentence we heard the other two shots. Then we realized or we thought it was gunfire, and then we could not at that point see the President's car. We were still moving slowly, and after the third shot the second two shots seemed much closer together than the first shot, than they were to the first shot. Then after the last shot, I guess all of us were just looking all around and I just looked straight up ahead of me which would have been looking at the School Book Depository and I noticed two Negro men in a window straining to see directly above them, and my eyes followed right on up to the window above them and I saw the rifle, or what looked like a rifle approximately half of weapon, I guess I saw. and just looked at it, it was drawn fairly slowly back into the building, and I saw no one in the window with it. I didn't even see a form in the window.
Iacoletti,
Maybe there was a plumber or an electrician up there, working during lunchtime, and maybe those two Black guys (Bonnie Ray Williams and Harold Norman) were just looking up there to see if he needed any help!
-- MWT

PS Or hey, maybe it was an evil, evil, evil CIA dude who stuck a section of pipe out there while Kennedy was goin' down Elm Street, and then set off a cherry bomb or somethin', just to help
frame Oswald after-the-fact!(I don't suppose Oswald or the Ruskie or Cuban assassin ducked down low so he couldn't be seen by nosey people down at street level before he started a-pullin' the barrel back through the window.)