It’s unlikely one shooter made three successful shots provided the angle and timeframe, but two shots is highly probable and has been reproduced in experiments.
The only thing missing is where one of those three shots came from. There is no further evidence at this point so everything further is conjecture. The most simple answer is a member of the secret service in extremely close proximity to the president misfired in a moment of panic after the first shot made contact with the President’s neck, which means the fatal head shot. Not dramatic enough for conspiracies but still embarrassing enough for a cover story.
You bastards.