That conclusion doesn't follow from the stated premises. The most basic missing premise is that Oswald was positioned (inside the book depository) behind the motorcade. See https://upload.wikimedia.org/wikipedia/commons/5/58/DealeyPl... Of course, there are many other necessary premises wherein lie the interminable debate. But if you assume (as it seems the doctor did) that at least one shot (possibly a miss) came from Oswald behind the president, who was facing forward; and one shot came from ahead of the president exiting the back of his head, the scenario the doctor believed the evidence demanded; then you must conclude at least two shooters.
Yeah, and Oswald shot perfect shots with a super old WW2 rifle in less than 10s while he was an average shooter at best based on what we know from him in the army. There's enough evidence at this stage to support several shooters despite what the History books claim.
