US 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.
Obama promised to make sure, quote, "whoever carried out this cowardly act is held responsible."
He said several people were shot Monday morning at the Washington Navy Yard about 3 1/2 miles (5 kilometers) from the White House, and some were killed.
He said the victims were "courageous Americans" who knew about the risks of serving overseas, but wouldn't have expected such "unimaginable violence" at home.
The White House says the president has been receiving frequent briefings about the unfolding situation by senior aides.