Aug. 3 (UPI) -- An attack outside the Pentagon on Tuesday left a police officer dead and multiple other people injured, prompting a temporary lockdown at the Arlington, Va., building, Defense Secretary Lloyd Austin announced.
The Pentagon Force Protection Agency tweeted earlier that there was an "active crime scene" and ordered the public to stay away from the Metro rail entrance and bus platform at the Defense Department headquarters.
A public affairs employee at the defense secretary's office told The New York Times a message read over the Pentagon's loudspeaker said there had been "a shooting incident at the Metro bus area."
The Arlington County Fire Department in Virginia tweeted that it "did encounter multiple patients."
The agency said the lockdown lasted for about 75 minutes and was lifted just after noon. The Metro entrance at the Pentagon, though, remained closed.
Austin said he ordered flags to be flown at half-staff at the Pentagon in response to the officer's death.
"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," Austin 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. We are forever grateful for that service and the courage with which it is rendered."
Austin said the Defense Department was investigating the incident.
Pentagon Force Protection Agency Chief Woodrow Kusse said gunfire was exchanged and there were "several casualties" in the attack, but declined to offer specific details on their condition.
"The Pentagon and the Pentagon reservation are safe and secure," he said during a briefing, adding there was no search for a suspect.
Sen. Mark Warner, D-Va., offered his condolences for the death of an officer involved.
"I'm incredibly saddened to learn about the passing of a Pentagon police officer, who was killed earlier this morning in a senseless act of violence outside the Pentagon. My heart goes out to the officer's family and friends, as well as the entire Pentagon Police force," he tweeted.