Section 100G. Any city operating under a Plan D or Plan E charter, by the affirmative vote of a majority of its city council or any other city, by a majority vote of its city council with the approval of its mayor, and any town, by a majority vote at an annual or special town meeting, shall pay the reasonable expense, not exceeding two thousand dollars, of the funeral and burial of any firefighter who while in the performance of his duty and as a result of an accident while responding to or returning from an alarm or fire or any emergency or as the result of an accident involving a fire department vehicle, which the firefighter is operating or in which he is riding or while at the scene of a fire or any emergency is killed or sustains injuries which result in his death, or of any police officer who while in the performance of his duty and as the result of an assault on his person, or a result of an accident while responding to an emergency while in the performance of his official duty or as result of an accident involving a police department vehicle which he is operating or in which he is riding is killed or sustains injuries which result in his death. The provisions of this section shall become effective in a city or town when accepted by such city or town.