Alvin Karpis was a notorious 1930s Depression-era gangster who taught a young Charles Manson how to play the guitar while they were both in federal prison. Karpis led the infamous Barker-Karpis gang alongside Fred and Doc Barker, committing bank robberies, kidnappings, and murders. The FBI named him "Public Enemy Number One" in the 1930s before his arrest in New Orleans in 1936. He served 26 years in prison—longer than any other inmate at the Alcatraz federal penitentiary.