A military base in Washington said it had lifted a lockdown imposed earlier on Friday because of a potentially armed person.
Joint Base Anacostia-Bolling, in southeast Washington, on its Facebook page had urged anyone who saw the person to run or hide.
"Barricade your door, turn off the lights and your cell phone ringer, and remain silent. If you are hiding, prepare to FIGHT," it said.
The base, which hosts the Defense Intelligence Agency headquarters, ended the lockdown by the middle of the afternoon, with the individual detained and set to be transferred to local police, according to the Facebook page.