In case of any vacancy from any cause in the office of mayor or any commissioner, the remaining members of the board of commissioners within 10 days after the occurrence of the vacancy shall elect some suitable person to fill the vacancy for the balance of the unexpired term of such office. If the remaining members cannot agree upon some such suitable person, then they shall call in the then city attorney who shall cast the decisive vote for such appointment. The resignation of the mayor or any commissioner elected under this act shall be made in writing for their action thereon. If the mayor or any commissioner shall remove from the territorial limits of the city, such removal shall ipso facto be deemed to create a vacancy in such person’s office.