White House spokeswoman Lindsay Walters said the decision was made Monday night “as soon as the president heard about the request from the mayor.”
She said that White House press secretary Sarah Huckabee Sanders spoke with Buckley both Monday night and Tuesday morning to alert him to the decision.
During a news conference on the Annapolis waterfront Tuesday morning, Buckley thanked Trump but relayed frustration over the process.
“We waited all of Saturday, all of Sunday,” Buckley said. “We understood maybe there was some communications problems. We waited all day Monday and didn’t hear anything.”
Before receiving a call from Sanders, Buckley said his understanding was that the request had been denied.
Four journalists and a sales associate were killed in the attack Thursday that police said was carried out by Jarrod Ramos, who had threatened employees of the paper before.
“We will never forget those names,” Buckley said. “We need the support community-based journalism brings.”
He said the city is planning a concert to celebrate the work of journalists.
In the White House proclamation, Trump said that the nation “shares the sorrow of those affected by the shooting at the Capital Gazette newspaper in Annapolis, Maryland.”
“Americans across the country are united in calling upon God to be with the victims and to bring aid and comfort to their families and friends.”
The proclamation ordered the flag at half-staff at the White House and all other federal buildings and grounds until sunset Tuesday. It also ordered the flag at half-staff for the same length of time at U.S. embassies, military facilities and other facilities abroad.
Maryland Gov. Larry Hogan (R) has also ordered state flags flown at half-mast. Buckley said Annapolis city flags would remain lowered until all the victims are buried.
The U.S. flag is flown at half-staff on federal buildings by presidential proclamation as a sign of respect after the deaths of public officials or noteworthy figures and after some mass shootings. In 2016, for example, it was flown at half-staff 53 times, including after mass killings in Orlando and Brussels. More recently, it flew at half-staff after 10 people were killed at a high school in Santa Fe, Tex.
Justin Wm. Moyer contributed to this report.