As a mark of respect for the victims of the senseless acts of violence perpetrated on September 16, 2013, at the Washington Navy Yard, President Obama has ordered the flag of the United States to 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 on 09-20-2013