Each commissioner shall be a citizen of the United States and a qualified elector of such city, and the removal from the city of any commissioner shall cause a vacancy in such office. In case a vacancy in the office of any commissioner occurs by resignation, death or any reason, the remaining commissioners shall within ten days after the occurrence of the vacancy, elect some suitable person to fill the vacancy until the next election, at which time a successor shall be elected to fill the unexpired term; provided, that there is any portion of such term unexpired. In case the remaining commissions cannot agree upon some suitable person for the office of commissioner, they shall then call in the city attorney, who shall cast the decisive vote for such appointment. (Prior code § 8-212)