The act has never been duplicated. That is a fact.
I don’t believe the conspiracy theories beyond, maybe Oswald wasn’t the shooter in the window. But, no doubt that the window in the Depository was the spot. After that, it’s just too easy for a reasonably competent shooter to kill him from that window. The head shot was to a certain degree the shooter getting one last round off before the limo got too far out of range, and a certain degree of “chance” that he happened to blow Kennedy’s head off.