In August 1792, a riot broke out in Paris. A crowd of protestors, encouraged by radical politicians, invaded the Tuileries. Louis was arrested on 13 August and sent to the Temple, an ancient Paris fortress used as a prison. On September 21, the National Convention (the new National Assembly) declared France to be a republic and abolished the monarchy. They took away Louis's titles and gave him an ordinary name: "Louis Capet". They believed that Capet should be his surname because he was related to the House of Capet.