After Missouri, Smith built the city of Nauvoo, Illinois as the new church headquarters, and served as the city's mayor and leader of the militia. As church leader, Smith also instituted the then-secret practice of plural marriage, and taught a form of Millennialism which he called "theodemocracy", to be led by a Council of Fifty which, allegedly, had secretly and symbolically anointed him as king of this Millennial theodemocracy. Partly in response to these trends, on June 7, 1844, a newspaper called the "Nauvoo Expositor", edited by dissident Mormon William Law, issued a scathing criticism of polygamy and Nauvoo theocratic government, including a call for church reform based on earlier Mormon principles. Considering the paper to be libellous, Smith and the Nauvoo city council voted to shut down the paper as a public nuisance. Relations between Mormons and residents of surrounding communities had been strained, and some of them instituted criminal charges against Smith for treason. Smith surrendered to police in the nearby Carthage, Illinois, and while in state custody, he and his brother Hyrum Smith, who was second in line to the church presidency, were killed in a firefight with an angry mob attacking the jail on June 27, 1844.