In accordance with a proclamation from President Joe Biden, the United States flag should be flown at half-staff March 23, 2021 through sunset on March 27, 2021 honoring the victims of the tragedy in Boulder, Colorado.
The Presidential Proclamation can be read here and below: https://www.whitehouse.gov/briefing-room/presidential-actions/2021/03/23/a-proclamation-honoring-the-victims-of-the-tragedy-in-boulder-colorado/
Original source can be found here.
