When making an arrest without a warrant, the officer shall inform the person to be arrested of his authority and the cause of the arrest, unless the person to be arrested is then engaged in the commission of an offense, or is pursued immediately after its commission or after an escape, or flees or forcibly resists before the officer has opportunity so to inform him, or when the giving of such information will imperil the arrest.
A.R.S. § 13-3888