President Obama on Tuesday ordered that the American flag at the White House and all public buildings and military posts be flown at half-staff until Saturday evening, to mark last week's shooting death of five servicemembers in Chattanooga, Tenn.

"Our thoughts and prayers as a nation are with the service members killed last week in Chattanooga," Obama said in a presidential proclamation. "We honor their service. We offer our gratitude to the police officers and first responders who stopped the rampage and saved lives. We draw strength from yet another American community that has come together with an unmistakable message to those who would try and do us harm: We do not give in to fear. You cannot divide us. And you will not change our way of life."

"As a mark of respect for the victims of the senseless acts of violence perpetrated on July 16, 2015, in Chattanooga, Tennessee ... 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, July 25, 2015."

The decision came just as some congressional Republicans were beginning to grumble that the White House had done nothing to mark the shooting. House Speaker John Boehner has ordered the U.S. Capitol flags to be flown at half-staff on Tuesday, but until shortly after noon on Tuesday, there was no sign from the White House that it would do the same.

"I don't have more information about the status of the flag over the White House," White House spokesman Josh Earnest said Monday when asked.

That response drew criticism from Republicans on Tuesday. Rep. Mac Thornberry, R-Texas, who chairs the House Armed Services Committee, called on Obama to follow the lead of the House.

"Last week, America lost five service members," he said. "They did not fall on a foreign battlefield, but were deliberately targeted and cruelly murdered here at home."

"Today, Speaker Boehner has ordered the flags at the Capitol to be flown at half-staff," he added. "He follows the governors of Tennessee and other states who are doing the right thing to honor those casualties. The president should follow suit and order flags flown at half-staff across the country, and he should do so immediately."

Rep. Marsha Blackburn, R-Tenn., said Tuesday morning there was no good explanation why the White House flags haven't been lowered yet.

"He is the commander in chief and for flags not to fly at half-staff is just beyond comprehension. This is a part of we as a nation grieving that members of our military were shot in the line of duty," the Republican said in an interview.

The shooting at a Navy and Marines Reserves Center in Chattanooga, Tenn., left four Marines dead last Thursday. Two days later, a Navy sailor died. The shooter, 24-year-old Mohammed Youssuf Abdulazeez, also exchanged fire with law enforcement at a Navy recruiting center, and was killed in a gunfight with law enforcement.

The shooting is being investigated as an act of domestic terrorism.