Jack Leon Ruby was an American nightclub owner. He fatally shot Lee Harvey Oswald on November 24, 1963, while Oswald was in police custody after being charged with both the assassination of John F. Kennedy, the incumbent United States president, and the murder of Dallas policeman J. D. Tippit. A Dallas jury found Ruby guilty of murdering Oswald, and he was sentenced to death.
Ruby's conviction was later appealed, and he was granted a new trial. However, as the date for his new trial was being set, Ruby became ill in prison and died of a pulmonary embolism from lung cancer on January 3, 1967.
In September 1964, the Warren Commission concluded that Ruby acted alone in killing Oswald. Various groups believed Ruby was involved with major figures in organized crime and that he killed Oswald as part of an overall plot surrounding the assassination of Kennedy.