David Sweat is a convicted murderer who led a famous 2015 prison break from the maximum-security Clinton Correctional Facility in Dannemora, New York. On June 6, 2015, Sweat and fellow inmate Richard Matt cut through their cell walls, crawled through underground steam pipes, and emerged through a manhole outside the prison. prison seamstress named Joyce "Tilly" Mitchell and a guard named Gene Palmer helped smuggle tools to the men.