At least 12 people have been killed - with several others injured - at a Navy yard in Washington.  A Navy official said two shooters were "down" after reports of shots fired at around 8:20 this morning at the Navy Sea Systems Command headquarters in the southeast part of the nation's capital.  

There are still conflicting reports on the number of shooters.  One is dead and the search continues for possibly 2 others.   There may have been as many as three shooters, including one in military fatigues.

Nearly 3,000 people work inside the building and were directed to stay in place.  Some low-flying helicopters were seen circling above the building, dropping baskets to help evacuate people from the complex.   President Obama has been briefed on the situation.