The flag of the United States shall be flown at half-staff on all buildings, grounds, and naval vessels of the Federal Government in the metropolitan area of the District of Columbia on the day of death and on the following day upon the death of a United States Senator, Representative, Territorial Delegate, or the Resident Commissioner from the Commonwealth of Puerto Rico, and it shall also be flown at half-staff on all buildings, grounds, and naval vessels of the Federal Government in the State, Congressional District, Territory, or Commonwealth of such Senator, Representative, Delegate, or Commissioner. respectively, from the day of death until interment.