Cullen Montgomery Baker was his name. Don't know what his nickname was. I've seen the account you gave pertaining to his death. Leon Metz, however, in his Encyclopedia of Lawmen, Outlaws, and Gunfighters states: "On 6 January, 1869, in Cass County, Thomas Orr, whom Baker had once tried to hang, allegedly killed him by lacing Baker's liquor with strichnine. Many years later, author Louis L'Amour memorialized Baker in his novel The First Fast Draw."
Good subject selection for your post.