This question has of course been the source of many a dispute and many a conspiracy theory. I recommend you take a look at the report of the Warren Commission, which concluded that Oswald was the sole assassin, as well as the report of the House Select Committee on Assassinations, which found that there were likely two gunmen. Both are available from the National Archives - the Warren Commission report is found at https://www.archives.gov/research/jfk/warren-commission-report , and the House select committee report is found at https://www.archives.gov/research/jfk/select-committee-report. Hopefully this information will be of value to you as you investigate this matter.
Dear Mr. Tucker,
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We searched the National Archives Catalog and located a series titled the Press and Public Contact Files, 2/1/1994 - 9/30/1998 in the Records of the Assassination Records Review Board (Record Group 541) that includes a file unit titled the Warren Commission Report which addresses the number of person involved. For information about these records, please contact the National Archives at College Park - Textual Reference (RDT2) via email at firstname.lastname@example.org.
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