President Barack Obama mourned yet another mass shooting in the U.S. that he said took the lives of American patriots. Obama promised to make sure “whoever carried out this cowardly act is held responsible.”

Todd Brundidge, an executive assistant with Navy Sea Systems Command, said he and other co-workers encountered a gunman in a long hallway on the third floor. The gunman was wearing all blue, he said.

“He just turned and started firing,” Brundidge said.

Terrie Durham, an executive assistant with the same agency, said she also saw the gunman firing toward her and Brundidge.

“He aimed high and missed,” she said. “He said nothing. As soon as I realized he was shooting, we just said, ‘Get out of the building.'”

Rick Mason, a civilian program-management analyst for the Navy, said a gunman was shooting from the overlook in the hallway outside his office.

Shortly after the gunfire, Mason said, someone on an overhead speaker 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 getting breakfast.

“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 several blocks away from the Navy Yard.

Ward said security officers started directing people out of the building with guns drawn.

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. A police officer and two civilian women were in critical condition at Washington Hospital Center, said Janis Orlowski, the hospital’s chief operating officer.

Orlowski said the police officer was in the operating room with gunshot wounds to the legs. The police chief said he was wounded when he engaged the shooter. It wasn’t clear if he shot at the gunman.

One woman had a gunshot wound to the shoulder. The other had gunshot wounds to the head and hand.

Anxious relatives and friends of those who work at the complex waited to hear from loved ones.

Tech Sgt. David Reyes, who works at Andrews Air Force Base, said he was waiting to pick up his wife, Dina, who was under lockdown in a building next to where the shooting happened. She sent him a text message about being on lockdown.

“They are under lockdown because they just don’t know,” Reyes said. “They have to check every building in there, and they have to check every room and just, of course, a lot of rooms and a lot of buildings.”

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. Only security personnel were allowed to be armed on the campus.

(AP)