Washington: A shooting rampage in the heart of a US Navy complex in Washington left at least 12 people dead on Monday. One shooter was killed, but police were looking for two other possible gunmen wearing military-style uniforms.
President Barack Obama said he is mourning "yet another mass shooting" and called it a "cowardly act".
Officials said at least four people were wounded - three critically - in the rampage at the Washington Navy Yard, including a law enforcement officer.
The shooting led to tightened security at the Capitol and White House nearby. D.C. Police Chief Cathy Lanier announced the death toll and said people were being told to stay in their homes and out of the area. "The big concern for us right now is, we potentially have two other shooters that we have not located," Lanier said. It was not immediately clear whether the number of dead included a gunman. Lanier said there was no indication of a possible motive.
Authorities identified the dead shooter as a Navy employee whose work status had been changed earlier this year, said a federal government official who spoke only on condition of anonymity because he wasn't authorised to speak on the record. While that may suggest the motive was job related, authorities haven't ruled out anything including terrorism, the official said.
Witnesses described a gunman firing down on a cafeteria from an upper floor and a gunman firing at people in a hallway on another floor. It wasn't clear whether the witnesses were describing the same gunman.
About 3,000 people work at the Naval Sea Systems Command headquarters, which builds, buys and maintains the Navy's ships and submarines and combat systems. Todd Brundidge said he and other co-workers encountered a gunman in a hallway on the third floor. The gunman was wearing all blue, he said. "He just turned and started firing," Brundidge said.
Terrie Durham added, "He aimed high and missed. He said nothing. As soon as I realized he was shooting, we just said, 'Get out of the building.'"
Rick Mason said a gunman was shooting from a fourth-floor overlook in the hallway outside his office. He said the gunman was aiming down at people in the building's cafeteria. Mason said he could hear the shots but could not see a gunman.
Mason said there are multiple levels of security to reach his office. That "makes me think it might have been someone who works here," he said.
Patricia Ward said she was in the cafeteria.
"It was three gunshots straight in a row - pop, pop, pop. Three seconds later, it was pop, pop, pop, pop, pop, so it was like about a total of seven gunshots, and we just started running," Ward told reporters.
One person died at George Washington University Hospital of a single gunshot wound to the left temple, said Dr. Babak Sarani, director of trauma and acute care surgery.
Janis Orlowski, chief operating officer of Washington Hospital Center, told reporters the hospital was treating three gunshot victims in critical condition. One was Washington police officer and two were civilian women.
Orlowski said the police officer had gunshot wounds to the legs. One woman had a gunshot wound to the shoulder, and the other had gunshot wounds to the head and hand.