UPDATE (3:33 p.m.): Officials say the Washington Navy Yard shooter who died after rampage has been identified as Aaron Alexis. There have been 12 confirmed deaths and Alexis', for a total of 13 dead. Officers are still searching for a second shooter.
Stay tuned to 6 News and CBS News for the latest on this story.
UPDATE (2:25 p.m.): Police say at least 12 people have died in the shootings at the Washington Navy Yard.
As many as three gunmen opened fire Monday inside one of the Navy's oldest buildings, attacking office workers at a heavily guarded military facility in the heart of the nation's capital.
Police are still searching for two additional suspects.
UPDATE (12:43 p.m.): President Barack Obama is mourning what he called, "yet another mass shooting" in the United States that he says took the life of American patriots. The shooting happened at the Washington Navy Yard, about three and a half miles from the White House.
President Obama promised to make sure, "whoever carried out this cowardly act is held responsible." He said the victims were "courageous Americans" who knew about the risks of serving overseas, but would not have expected such 'unimaginable violence" at home.
UPDATE (12:40 p.m.): Police are looking for two additional suspects in the shooting rampage at the Washington Navy Yard.
Witnesses reported seeing two additional gunmen, both dressed in military-style clothing, said Cathy Lanier, District of Columbia Police Chief. Lanier says one police officer was injured in an exhange of gunfire with a shooter and that one shooter has been killed.
Two Navy officials say at least six people were killed in the rampage. Four people have been taken to hospitals.
UPDATE (10:32 a.m.): CBS News is reporting that at least three people are dead and as many as 10 people are injured following the shooting.
There are some reports - still unconfirmed - that there could be more than one gunman.
ORIGINAL STORY: The Navy says several people have been injured in a shooting at a building at the Washington Navy Yard.
There's word that some people have been killed and that the shooter has been "contained" - though not in custody.
Officials say the shots were fired at around 8:20 a.m. at the Naval Sea Systems Command headquarters, where about 3,000 people work.
Police and federal agents are on the scene. Ambulances are parked outside the building, and streets in the area are closed. Flights at Reagan National Airport have been temporarily halted.
A U.S. Park Police helicopter hovered over the building and appeared to drop a basket or a stretcher with a person onto the roof.
Naval Sea Systems Command is the largest of the Navy's five system commands and accounts for a quarter of the Navy's entire budget. It builds, buys and maintains the Navy's ships and submarines and their combat systems.
President Barack Obama is getting frequent briefings on a shooting at the Washington Navy Yard.
The White House says the president had several briefings about the unfolding situation by senior aides.