What crime did machine gun Kelly go to Alcatraz?

Machine Gun Kelly, whose real name was George Kelly Barnes, was incarcerated at Alcatraz for kidnapping and extortion. He was involved in the kidnapping of a wealthy oil magnate's family member in 1933, which ultimately led to his capture and conviction. Kelly's notorious reputation as a gangster and his use of a Thompson submachine gun contributed to his infamous persona during the Prohibition era. He was sentenced to 17 years in prison and sent to Alcatraz in 1934, where he remained until 1951.