Mitchell Guist, one of the stars of the History Channel reality series Swamp People, died Monday night, a Louisiana sheriff said. Assumption Parish Sheriff Mike Waguespack said Guist had fallen while aboard his boat on the Intercoastal Waterway, near Pierre Part, La. The cause of his fall, and the cause of his death, is still unknown. Swamp People features residents of Louisiana’s Atchafalaya swamp country during alligator-hunting season. The network said Guist turned 49 on Friday.