A Pentagon spokesman, John Kirby, said Lloyd J. Austin III, the secretary of defense, was at a regularly scheduled meeting with President Biden at the White House at the time of the attack, and was immediately notified by his staff that it had taken place.
The secretary later traveled to the Pentagon and visited the building’s operations center upon his arrival, Mr. Kirby said.
Soon after the Pentagon acknowledged the death of the officer, Mr. Austin released a statement that said that flags at the Pentagon would be flown at half-staff.
“This fallen officer died in the line of duty, helping protect the tens of thousands of people who work in — and who visit — the Pentagon on a daily basis,” the statement said. “He and his fellow officers are members of the Pentagon family, and known to us all as professional, skilled and brave.”
“This tragic death today is a stark reminder of the dangers they face and the sacrifices they make,” he added. “We are forever grateful for that service and the courage with which it is rendered.”
The scene was secured just before noon, officials said, and a message posted on Twitter announced that the building had reopened, but said the Metro entrance remained closed. According to a public affairs employee in the secretary of defense’s office, a message was read over the Pentagon’s loudspeaker system around 10:45 a.m. stating that there had been “a shooting incident at the Metro bus area” and instructing employees to “stay in the building until further notice.”
The announcement was followed by a similar alert sent to all computer terminals in the Pentagon about 15 minutes later.
Chief Kusse said that the last major attack on the Pentagon’s Metro entrance was in March 2010, when John Patrick Bedell pulled out two 9-millimeter semiautomatic weapons and began shooting at the security checkpoint near the entrance to the Pentagon subway station, wounding two officers. Mr. Bedell was shot and killed by security officers.
Michael S. Schmidt contributed reporting.