Didn't realize there was such a clear view of the exact corner of the picket fence (from the Zapruder film). So we know there was no one at the exact corner. Of course Lane and Holland and the HSCA suggested the shooter might have been about 8 feet from the corner of the fence. Which is convenient as there is a tree blocking that view.
Lane's first theory was that one or more of the shots came from the Triple Underpass bridge. Sam Holland originally said it
might have been a shot but he didn't see a rifleman.
"There was a shot, a report, I don’t know whether it was a shot.
I can’t say that. And a puff of smoke came out about 6 or 8 feet
above the ground right out from under those trees. And at just
about this location from where I was standing you could see
that puff of smoke, like someone had thrown a firecracker,
or something out, and that is just about the way it sounded.
It wasn't as loud as the previous reports or shots."
Holland compared the "puff of smoke" to a firecracker, steam and cigarette smoke. Sitzman witnessed a soda pop bottle being broken which might explain the "shot" Holland heard, as well as the indistinct visual event he could never recall with detail (the bottle-breaking was in Holland's line-of-sight). Only in 1966, after being in contact with Mark Lane and Josiah Thompson, did Holland begin to start talking about a rifleman at the fence.
There was only one line of bushes between Sitzman and the back of the fence, which was sunlit and could be seen through openings in the foliage. The fence area to the right of the Zapruder frames show the open area beneath the foliage continuing, then an area with no bushes between Sitzman and the parking lot area.