Jack Ruby was born to Polish immigrant parents in Chicago in 1911. Various conflicting birth dates, from March to June of that year, are quoted in various sources and were given by Ruby at various times. The fifth of his parents' eight living children, he had a troubled childhood and adolescence, marked by juvenile deliquency and times in foster homes. Young Ruby worked selling horse-racing tip sheets, then for a scrap-iron collectors union; he was rumored to have minor links to organized crime. He served in the military during World War II without seeing combat. After being discharged he moved to Dallas and worked managing nightclubs, strip clubs, and dance halls, and also working as manager for entertainers.
Ruby often carried a handgun. He came to major national attention when he shot Oswald, which he claimed was a spur of the moment action taken when the opportunity presented itself. The killing was shown live on national television, the first such incident in the United States. Oswald was being transferred from one jail to another at the time. The gun used by Ruby was a Colt Cobra revolver of .38 Special caliber, serial number 2744 LW.
There has been much debate about Ruby's motives. He claimed that he killed Oswald in order to save Jacqueline Kennedy from testifying in a murder trial. Other people suggest that he was carrying out a Mafia "hit" (there is some evidence to support his having strong crime syndicate links), or that he was part of a conspiracy to assassinate the president and silenced Oswald to prevent him from testifying. Much suspicion was aroused by the fact that he was able to freely enter a supposedly secure area, armed with a pistol, minutes prior to the alleged assassin of the President of the United States being transferred out. However, others have pointed out that Ruby was an unstable man who revered Kennedy and was seeking vengeance of his own accord. They point to the fact that Ruby had only just arrived at the police station, having wired money to an employee, whilst Oswald's movement had been delayed, due to his changing clothes.
Ruby was tried and on March 14, 1964 was convicted of Oswald's murder. In an appeal to the Texas Supreme Court, it was argued that Ruby could not have gotten a fair trial in the city of Dallas due to the excessive publicity surrounding the case. The appellate court ruled that his motion for a change of venue before the original trial court should have been granted for that very reason, and overturned his conviction and death sentence. He died of a pulmonary embolism in prison on January 3, 1967 before he could be re-tried. He is buried in the Westlawn Cemetery in Chicago, Illinois.