Jack Leon Ruby, March 25, 1911–January 3, 1967 was a Dallas,Texas nightclub owner who fatally shot Lee Harvey Oswald on November 24, 1963,. While Oswald was in police custody after being charged with assassinating U.S. President John F. Kennedy two days earlier. A Dallas jury found him guilty of murder and he was sentenced to death. Ruby's conviction was later appealed and he was granted a new trial. However, on January 3, 1967, as the date for his new trial was being set, Ruby became ill in his prison cell and died of a pulmonary embolism from lung cancer.

November 24, Ruby drove into town with his two pet dogs. He walked to the nearby Dallas police headquarters, where he made his way to the basement via either the Main Street ramp or a stairway accessible from an alleyway next to the Dallas Municipal Building. At 11:21 am CST — while authorities were escorting Oswald through the police basement to an armored car that was to take him to the nearby county jail — Ruby stepped out from a crowd of reporters and fired a single round from his .38 revolver into Oswald's abdomen, fatally wounding him. Ruby was immediately subdued by the police. The shooting was broadcast live nationally, millions of television viewers witnessed it. Oswald was taken unconscious by ambulance to Parkland Memorial Hospital—the same hospital where doctors tried to save President Kennedy's life two days earlier. Oswald died at 1:07 pm. Ruby's reason for the killing was he had killed his President.

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