In order to make an arrest, a peace officer, who has announced his authority and purpose, may break open an outer or inner door or window of any vehicle, watercraft, aircraft, dwelling or other structure, movable or immovable, where the person to be arrested is or is reasonably believed to be, if he is refused or otherwise obstructed from admittance. The peace officer need not announce his authority and purpose when to do so would imperil the arrest.