There was only a single bullet. If not, a researcher would have to find all the possible trajectories and origins of any other bullets which caused such damage.
No one and I repeat no one has ever been able to explain any other bullets, their trajectories and sources.
Nobody has been able to explain how one bullet could do all the things it would have to have done either.
Years later Gerald Ford admitted changing some of the trajectory detail to make that theory work.
To be honest, I don't remember the particulars associated with that since it's been awhile.