If any persons to the number of twelve or more, being armed with clubs or other weapons. . . shall be unlawfully, riotously, or tumultuously assembled . . . (Read riot act, if don’t disperse) . . . It shall be lawful for every officer . . . to seize such persons, and carry them before a justice of the peace; and if such persons shall be killed or hurt by reason of their resisting . . . officers and their assistants shall be indemnified and held guiltless.