FWIW: methinks the “grassy knoll shots” was the result of a half-circle structure at that location, focusing an echo of the passing rounds (from Oswald) onto a point at that location and giving the auditory illusion of shots being fired from there. Most people do not understand how much noise a passing bullet makes, how long it takes to travel, and how the local architecture affected those facts.
The Pergola is the half-circle structure, I always forget the word myself, seen in a map of Dealy Plaza.
