Section 99F. The powers, duties and liabilities of a regional police district shall be vested in and exercised by a regional police district commission organized by the boards of selectmen of the member towns. Each said board shall appoint two members of the commission within three months of the adoption of the regional police district law, for terms of such length and so arranged that the term of one appointee will expire each year, and their successors shall be appointed in a like manner for terms of two years. Vacancies shall be filled in a like manner for the unexpired term. All members shall serve without compensation but may be reimbursed for expenses actually incurred in the transaction of the business of the commission. The commission shall choose annually a chairman and a vice chairman by ballot from its membership. The vice chairman shall, in the absence of the chairman, exercise the powers and perform the duties of said chairman. It shall appoint a secretary and a treasurer who may be the same person, but who need not be members of said commission. The treasurer shall receive and take charge of all money belonging to the district, and shall pay any bill of the district which shall have been approved by the commission. The commission may appoint an assistant treasurer who need not be a member of the commission, and who shall, in the absence of the treasurer, perform his duties and shall have the powers and be subject to the requirements and penalties applicable to him. The treasurer and assistant treasurer may, by vote of said commission, be compensated for their services. The treasurer and assistant treasurer of said district shall be subject to the provisions of sections thirty-five, fifty-two and one hundred and nine A of chapter forty-one, to the extent applicable. If the office of secretary is vacant or if the secretary is absent or is unable to perform his duties because of disability, the commission may appoint a temporary secretary to hold such office and exercise the powers and perform the duties thereof until a secretary is duly appointed or the secretary who was disabled or absent resumes his duties.