N.H. Rev. Stat. Ann. § 47:14

They shall appoint a city marshal, and one or more assistant marshals if they think it necessary, a collector of taxes, constables, police officers and watchmen, and may remove them from office for sufficient cause; and may require the marshal and constables, before entering on their duties, to give bonds, with sufficient sureties to any reasonable amount, upon which like proceedings and remedies may be had as in case of bonds required to be given by constables of towns.