Any county, city, or town may provide for the relief of any children and surviving spouse of any law-enforcement officer, sheriff, or deputy sheriff who dies while in the service of the county, city, or town. If any policeman loses his life while in the discharge of official duties, there shall be paid to the surviving spouse until death, or remarriage, a pension of not less than one-half of the policeman’s salary at the time of death. The relief provided shall be exclusive of any payment out of the general fund of the state treasury pursuant to § 9.1-400 et seq.