WASHINGTON -- Multiple people were killed and several more wounded when at least one gunman opened fire Monday at the Naval Sea Systems Command headquarters, authorities said.
The Navy said "several" people were killed at the Navy Yard. Ed Buclatin, the public affairs chief for the Navy Installations Command, tweeted "four killed and eight injured." He also tweeted that reports of more than one shooter had not been confirmed.
The situation was fluid. The Associated Press reported that a shooter had been "contained" in the building but was not in custody, according to a Defense Department official who spoke to AP on condition of anonymity.
WUSA-TV in Washington, citing Naval District of Washington spokesman Ed Ziegler, said four people were killed, eight more wounded and that two shooters were "down" in the building.
A federal law enforcement official told USA TODAY that authorities have not ruled out the possibility of multiple shooters. The official who had been briefed on the matter said there were conflicting reports on the number of fatalities.
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Rick Mason, a program management analyst who is a civilian for the Navy, 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 on the first floor. Mason said he could hear the shots but could not see a gunman.
Shortly after the gunfire, Mason said overhead speakers told workers to seek shelter and later to head for the gates at the complex.
Patricia Ward, a logistics management specialist,said she was in the cafeteria. "I heard three shots -- pow, pow, pow. Thirty seconds later I heard four more shots."
Then panic, as people tried to get out of the cafeteria. "A lot of people were just panicking. There were no screams or anything because we were in shock."
The first news broke with the Navy reporting on its Twitter feed that there was an "active shooter" at Building 197 at the Navy Yard, and that three shots had been fired at 8:20 a.m. ET. The Navy later reported deaths and injuries, but details remained fluid.