Rules on Criminal Procedure
Section 9. Method of arrest by private person. - When making an arrest, a private person shall inform the person to be arrested of the intention to arrest him and cause of the arrest, unless the latter is either engaged in the commission of an offense, is pursued immediately after its commission, or has escaped, flees, or forcibly resists before the person making the arrest has opportunity to so inform him, or when the giving of such information will imperil the arrest. (9a)