A suspect has been taken into custody after also being shot during the incident. The location of the attack near the White House is said to be secure.
The Secretary of Defence Pete Hegseth says President Donald Trump has asked him to send 500 additional National Guard troops to Washington DC following the attack.
West Virginia's Governor Patrick Morrisey earlier said both National Guard members had died, before posting that he was hearing "conflicting reports" about their condition.
Clive Myrie presents breaking News at Ten reporting from Sarah Smith and Tom Bateman in Washington.