Associated Press: Rick Mason, a program management analyst who is a civilian with the U.S. 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 and heard shots. They sounded like "pop, pop, pop," she said. After a few seconds, there were more shots, she said.
"Everybody just panicked at first," she said. "It was just people running, running, running."
Ward said security officers started directing people out of the building with guns drawn.