On the second Monday of January next following the adoption of the board under the provisions of this act and thereafter, the law enforcement agency shall assume and shall exercise all powers, duties and responsibilities previously exercised by the sheriff and deputies of the sheriff. The sheriff, upon demand of the board, shall transfer and deliver to the agency all vehicles, property and records belonging to the sheriff’s department. A record of all property so transferred shall be prepared and copies thereof filed in the office of the county clerk and with the secretary of the board. On the date fixed for the transfer of such authority, those officers and employees of the sheriff of the county specified in Kan. Stat. Ann. § 19-4476 who have not previously joined the agency shall become members of the department if they so elect: Provided, That such officers and employees shall have filed in writing with the director a request to transfer at least fifteen (15) days prior to such transfer date.