That Oswald did it is pretty obvious.
Easy shot for a marine.
There is reason to consider that a Secret Service agent may have subsequently had a very unfortunately directed negligent discharge, confusing subsequent examination & explanation.
WHY Oswald did it apparently remains in doubt.
Whether it was a “Professor Raoul X” scenario, or some nut followed his dreams to a conclusion, will remain hard to discern.
Was in Dallas and looked out the window at the X in the street. Easy shot any hunter.