A gunman appeared to ambush two National Guard troops and reportedly fired three shots at them during an exchange of gunfire that left two in critical condition.
Video showed the attack, just one block away from the White House, with a suspect walking up to the troops before firing at them, CNN reporter Evan Perez said.
The two troops, whose conditions are uncertain following conflicting reports that they had died, were seriously injured. At least one was shot in the head, and at least one was airlifted.
The investigation was developing. West Virginia Gov. Patrick Morrisey initially announced their deaths on X, but walked back the announcement.
The suspect, whose name has not been released, is still alive. He appeared to have been injured after one of the troops fired back at him or when glass from a bus stop area broke nearby.
D.C. Police, FBI and the Secret Service were investigating.