President Obama has ordered that flags be lowered to half-staff at the White House and federal buildings across the country to honor the victims of last week's shooting rampage in Chattanooga, Tenn., after facing pressure from lawmakers and others. 

In a proclamation issued early Tuesday afternoon, Obama said of the Chattanooga victims, "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." 

He ordered flags flown at half-staff at the White House and "all public buildings and grounds," as well as over military posts and naval stations and vessels -- until July 25. Flags will be flown at half-staff at U.S. embassies and other overseas diplomatic offices. 

The decision comes after congressional leaders ordered flags at the U.S. Capitol lowered to half-staff earlier in the day -- that decision fueled questions over why the White House hadn't yet done the same. 

Rep. Duncan Hunter, R-Calif., a veteran, earlier released a statement calling it "unconscionable" that the flags had not been lowered, as of Tuesday morning. "The flag and all it represents is sacred to our military, and the President must know that lowering the flag is a signal of honor and respect," he said. 

Shortly afterward, the White House issued its proclamation, following similar instructions for the Capitol by Senate Majority Leader Mitch McConnell and House Speaker John Boehner. 

"Last week, five brave service members were murdered in a terror attack in Chattanooga, Tennessee. Out of respect for their courageous service and sacrifice to our nation, flags at the U.S. Capitol are being lowered to half-staff," Boehner said in a statement. 

The House will also observe a moment of silence Tuesday evening for the victims. 

McConnell said, "[T]he U.S. Senate's thoughts are with their families and loved ones, and with all those who protect us here, and around the world." 

The shooting occurred at two military facilities. A Navy sailor and four Marines were killed. 

The White House has ordered flags lowered on several occasions in the past, including after the tragic mass shooting in December 2012 at an elementary school in Newtown, Conn. The directive at the time ordered flags lowered, "As a mark of respect for the victims of the senseless acts of violence perpetrated on Dec. 14, 2012, in Newtown, Conn." 

Asked about the status of the White House flags on Monday, Press Secretary Josh Earnest told reporters that Obama has offered his "sincere condolences to the families of those who were killed in this attack," without mentioning the forthcoming proclamation.  

The shooting has prompted governors in at least a half-dozen states to authorize National Guardsmen to take up arms to protect recruiting offices and installations. 

The U.S. military also has outlined security upgrades for recruiting stations, reserve centers and other facilities, according to Capt. Scott Miller, a spokesman for the U.S. Northern Command, which covers military bases in North America. 

The Associated Press contributed to this report.