Tex. Code Crim. Proc. art. 6.03

Whenever, in the presence or within the observation of a magistrate, an attempt is made by one person to inflict an injury upon himself or to the person or property of another, including the person or property of his spouse, it is his duty to use all lawful means to prevent the injury. This may be done, either by verbal order to a peace officer to interfere and prevent the injury, or by the issuance of an order of arrest against the offender, or by arresting the offender; for which purpose he may call upon all persons present to assist in making the arrest.