By Ian Simpson
WASHINGTON (Reuters) - Sam Agger, 60, was just starting his regular Monday morning meeting with colleagues in a fourth floor conference room at Washington's Navy Yard when he heard a "big bang."
A program analyst supporting Navy radar programs, Agger said he realized immediately it was a gunshot. He and five of his colleagues locked the door and piled furniture against it.
"It was loud and different, particularly when there was a second such distinctive noise," he said. "It was terrifying. It was one of the worst days of my life."
The shooting rampage launched by Aaron Alexis, 34, a tech contractor and former Navy reservist, took the lives of 12 victims before he was shot dead by police. The bloodshed prompted a review of global U.S. military security.
Earlier that morning, Alexis drove to the Navy Yard and left his car, which was not searched, in one of the parking garages. The previous night he had stayed less than 2 miles away at a Residence Inn, a hotel he had moved into weeks earlier.
Using a valid security pass from his employer, he entered the building armed with a 12-gauge shotgun, which an employee at Sharpshooters Indoor Shooting Range and Pro Shop in Lorton, Virginia, said he had purchased two days earlier. He had also bought three boxes of ammunition, according to the employee.
The first gunshot rang out around 8:15 that morning, according to witnesses. It sounded like "a locker door slamming," said one, a former military officer working at the yard.
More shots followed within minutes, and quickly transformed the orderly military facility, a square, brick building into a scene of carnage and chaos.
Standing in the fourth-floor atrium of Building 197, just down a hall from where Doug Hughes and a co-worker had barricaded themselves behind a door, Alexis began shooting. His targets were employees eating breakfast in a cafeteria below.
All told he had three guns, one of which he took from a security guard whom he shot, according to a federal law enforcement source.
Warnings rang out over the building's loudspeakers.
Agger said he and his co-workers lay low, listening to the repeated announcements: "'Attention, there has been a fire in the building. Please do not take the elevator, take the stairs.' Over and over again, and really, really loud."
Some people ran in panic, one person tore a hamstring trying to get away. Others climbed walls.
"Two men, one of them in Navy fatigues, came running at me and said, 'Clear the building, clear the building, there's a shooter,'" said Janice Burford, 51, of Arlington, Virginia, a Navy contractor working in Building 197.
"We tried to escape out of the area," said the former military officer.
A man wearing a badge guided people into a parking garage which had been turned into a triage area for the wounded.
The shooting spree, which took place in the lobby and on the third and fourth floors, lasted about 30 minutes, Metropolitan Police said.
Agger's group was led out by police down corridors splattered with blood.
"Like you're doing a paint job, you mess up," Agger said.
He saw a woman's body, in a dress, lying on her side and face down. He believed she was dead.
"One of her shoes was off, it was a high-heeled shoe," Agger said.
Some people were led to a gathering place where Disney movies rather than news programs were playing because authorities "didn't want to stress people out," said one woman.
In one building, security forces entered at 4 p.m. and ordered all occupants to leave with their hands up, one worker said. They were marched to a conference center on the yard, given food and water and interviewed by the FBI.
As night fell and the interviews were completed, the employees climbed onto buses to head for a parking lot at nearby Nationals Park baseball stadium and into the arms of their families waiting there, ready to take them home.
Agger said he walked out with his computer, as did his colleagues, and everything but his tie.
"My tie is still in that room. I took off my tie as this was happening because of some weird notion that tourniquets are important," he said.
(Additional reporting by David Alexander, Margaret Chadbourn, Susan Cornwell, Emily Stephenson, Alina Selyukh, Mark Hosenball; Writing by Barbara Goldberg; Editing by Dina Kyriakidou and Mohammad Zargham)