Minutes into a news briefing, Trump was taken out of the room with no explanation for the disruption. Treasury Secretary Steve Mnuchin and Office of Management and Budget Director Russ Vought were also taken out of the room and the doors were locked.
Trump was heard to say "Oh!" and "What's happening", as he left the briefing room.
When Trump returned, he said there was a shooting outside of the White House premises.
He said the person was shot by the Secret Service or law enforcement and he was taken to the Oval Office after the incident.
"It was a shooting outside of the White House," Trump 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."
Nobody else was wounded in the shooting, Trump said. He praised the Secret Service response and said the agency would have more details on the event later.
"There were no details - we just found out just now," Trump told reporters.
The Secret Service did not immediately respond to queries about the incident.
He said the shooting was nearby the White House but outside the perimeter gates.
Trump said he understood the suspect was armed.
He said he feels very safe at the White House with the Secret Service.