Writers of historical fiction are not under the same obligation as historians to find evidence for the statements they make. For us it is sufficient if what we say can't be disproved or shown to be false. ↗
The original judgment of the FBI, the Secret Service, and the CIA was that there were three shots. I don't think that convinced us except as a statement by people, many of them who were familiar with ballistics. This question troubled me greatly. ↗