A police officer was killed and several other people were injured in an attack outside the Pentagon on Tuesday, forcing the building to go briefly into lockdown, officials said.
The Pentagon Force Protection Agency said an officer had been killed at a public bus stop outside the building in Arlington, Virginia, but the cause of death was not released.
Chief Woodrow Kusse, head of the Pentagon's police force, told reporters several people were injured in the incident.
Kusse declined to speculate on a motive for the attack or to say whether the assailant was in custody, but added that authorities were not actively looking for one.
He said the FBI was assisting in the investigation.
The building was briefly put on lockdown as police responded to the incident.
"I have ordered to half-mast the flags flown on the Pentagon Reservation in honor of his loss," U.S. Defense Secretary Lloyd Austin said.