UPDATE #4: At least six are dead, according to Associated Press. In addition, Mayor Gray and D.C. Police Chief Lanier have stated that there are two additional shooters that may be on the loose.
UPDATE #3: One shooter is reported dead.
UPDATE #2: There are now reportedly 3 shooters.
UPDATE: Even as this story is released, new reports are saying that there are at least 4 killed and 8 wounded. In addition, the shooter has apparently barricaded himself in one of the buildings in the area.
From Washington Post:
As hundreds of police officers from various agencies converged on the scene, officials at Reagan National Airport ordered all outgoing flights held.
Police on the scene said eight civilians were shot, along with the two police officers. One is a D.C. Metro Police officer who was shot two times in the leg, police said. The other officer worked at the base.
A Navy Yard employee reached by telephone shortly before 10 a.m. said employees are still being told to shelter in place. She did not hear the shots, but described sirens, SWAT teams, Marines and a helicopter responding.
The U.S. Navy said that three shots were fired around 8:20 a.m. at the Naval Sea Systems Command Headquarters building, where about 3,000 people work.
Police closed the 11th St Bridge as well as M St SE between 2nd and 4th streets SE due to the shooting. Entrances to the Navy Yard Metro station remain open.
U.S. Capitol Police confirmed enhanced security at the Capitol, but no immediate threat.
Tyler Elementary School at 10th and G streets in Southeast is on lockdown.
As helicopters circled overhead and emergency vehicles continued to rush to the scene, crowds of onlookers gathered on sidewalks and at a construction site near the Navy Yard, but police pushed them back, yelling at them to keep a distance from the grounds.
One employee who declined to give his name said he heard “blam, blam” inside one of the buildings, then someone pulled the fire alarm.
“We aren’t going back on base today,” he said. “[But] there are still people inside.”
Reports began circulating around 9:30 a.m. that the suspect was “down,” but D.C. police said the suspect is still on the loose and “hiding between floors.”