In addition to any other benefits provided for in this chapter, upon the death, on or after January 1, 1959, and before retirement, of any member who, at the time of his or her death was a legislator, there shall be paid to his or her beneficiary, if he or she has designated one, and if not, to his or her estate, an amount equal to the annual compensation payable to him or her during the 12 months immediately preceding his or her death.