As a mark of respect for the victims of the senseless acts of violence perpetrated on May 24, 2022, by a gunman at Robb Elementary School in Uvalde, Texas, by the authority vested in me as President of the United States by the Constitution and the laws of the United States of America, I hereby order that the flag of the United States shall be flown at half-staff at the White House and upon all public buildings and grounds, at all military posts and naval stations, and on all naval vessels of the Federal Government in the District of Columbia and throughout the United States and its Territories and possessions until sunset, May 28, 2022. I also direct that the flag shall be flown at half-staff for the same length of time at all United States embassies, legations, consular offices, and other facilities abroad, including all military facilities and naval vessels and stations.
IN WITNESS WHEREOF, I have hereunto set my hand this twenty-fourth day of May, in the year of our Lord two thousand twenty-two, and of the Independence of the United States of America the two hundred and forty-sixth.
JOSEPH R. BIDEN JR.
Read on the white house website
Flags on poles are flown at half-mast. If you cannot lower a flag then a mourning ribbon can be placed on the American flag.