US President Donald Trump has said someone was shot near the White House, after abruptly leaving a news conference.
Mr Trump told reporters the incident "seems very well under control".
He reappeared moments after a member of his security detail had walked on stage during his remarks to reporters and escorted him out.
Mr Trump was heard to say "Oh!" and "What's happening", as he left the briefing room.
The president was interrupted mid-sentence by an agent whispering in his ear at the podium during Monday's incident.
When he returned about nine minutes later, the president told reporters he believed the US Secret Service had shot a suspect, who was armed "from what I understand".
He said that someone was taken to hospital after the incident.
Mr Trump acknowledged it was an unusual situation, but praised the professionalism of the Secret Service.
"It was a shooting outside of the White House," the Republican president said. "It seems to be very well under control.
"But there was an actual shooting, and somebody has been taken to the hospital. I don't know the condition of the person."
The US Secret Service meanwhile tweeted: "The Secret Service can confirm there has been an officer involved shooting at 17th Street and Pennsylvania Ave.
"Law enforcement officials are on the scene. More information to follow."
Mr Trump told reporters he did not know if the suspect harboured any ill intentions towards him.
"It might not have had anything to do with me," the president said.
A journalist asked Mr Trump if he was rattled by the incident.
"Do I seem rattled?" he replied.
The president added: "It's unfortunate that this is the world, but the world's always been a dangerous place. It's not something that's unique.
"The world has been, if you look back over the centuries, the world has been a dangerous place, very dangerous place, and it will continue, I guess, for a period of time."
He told journalists he was escorted to the Oval Office outside the briefing room during the incident.
Also led out of the news conference were Treasury Secretary Steve Mnuchin and Office of Management and Budget Director Russ Vought.
The doors were locked.