On November 22, 1963, MacNeil was covering President John F. Kennedy's visit to Dallas for NBC News. After shots rang out in Dealey Plaza, MacNeil, who was with the presidential motorcade, followed crowds running onto the Grassy Knoll (he appears in a photo taken just moments after the assassination). He then headed toward the nearest building and encountered a young man leaving the Texas School Book Depository at around 12:33PM CST. He asked the man where the nearest telephone was and the man pointed and went on his way. MacNeil later learned the man he encountered might have been Lee Harvey Oswald. Historian William Manchester reached this conclusion in his book "The Death of a President" (1967). Recounting the day's events to the Dallas Police, Oswald may have mistaken MacNeil for a Secret Service agent because of his suit, blond crew cut, and press badge. MacNeil has said, "it was possible, but I had no way of confirming that either of the young men I had spoken to was Oswald."