Upon the filing of the petition under section 71-921, the clerk of the district court shall cause a summons fixing the time and place for a hearing to be prepared and issued to the sheriff for service. The sheriff shall personally serve upon the subject and the subject’s legal guardian or custodian, if any, the summons and copies of the petition, the list of rights provided by sections 71-943 to 71-960, and a list of the names, addresses, and telephone numbers of mental health professionals in that immediate vicinity by whom the subject may be evaluated prior to his or her hearing. The summons shall fix a time for the hearing within seven calendar days after the subject has been taken into emergency protective custody. The failure of a subject to appear as required under this section shall constitute grounds for the issuance by the mental health board of a warrant for his or her custody.