If benefits are payable under this chapter because of an injury to, or the death of, a member of the retirement association, and such injury or death is the proximate consequence of the act of any person other than his employer, the board on behalf of the retirement association may recover from such person an amount which is the lesser of the following:
(1) An amount which is equal to one-half of the actuarial equivalent of the benefits for which the association is liable because of such injury or death; or
(2) An amount which is equal to one-half of the remaining balance of the amount recovered after allowance of that amount which the employer or its insurance carrier have paid or become obligated to pay. The right shall be determined under the subrogation provisions of any workmen’s compensation law.