Fortunately, Hill gave us several critical clues. This is from his
original treasury dept. report, as he described the first of the two shots
he heard:

"On the left hand side was a grass area with a few people scattered along
it observing the motorcade passing, and I was visually scanning these
people when I heard a noise similar to a firecracker..."

Hill gives us two clues here. First, he tells us that he was turned to his
left and scanning a small group in a grassy area when the first of those
two shots was fired.

All we have to do then, is to look at Hill in the Zfilm and try to figure
out when he turned to his left to scan those people. But here, we run into
a problem. I have looked at him in extreme blowups in the MPI DVD and
cannot see him ever doing such a thing.