If I may, I will comment on the relevance of an actual visit to the crime scene. I have been there. Stayed longer than expected and received a parking ticket to prove it.
What impressed me immediately is that the place was much smaller than expected. The plaza photographs large, but in fact is a very tight space.
I walked the grounds, and visited the Sixth Floor museum. At that time the location of the bubble top at the time of each known shot was marked on the pavement, making reconstruction easy for visitors. The shot set-up from the sixth floor is quite good. At the time of the last shot the distance to target is not great, target is moving almost directly away from the shooter at low speed. This is not a difficult shot.
By contrast, the behind the fence location is much more problematic. It is actually quite exposed. The shooter would have been visible from several angles. Not a location a professional would have chosen, in my opinion. This is a "passing shot", with the target moving laterally, with a variable speed. At the time of the final shot a shooter at that location would have been at a high angle to the right of target, giving a trajectory that does not match the injuries to the head.
My opinions on the shooting aspects are based on my experience as a trained military shooter, weapons and tactics NCO and civilian small arms instructor.
