Navy Capt. Mark Vandroff had begun a meeting to prepare for a presentation at the Pentagon.
"It was a very normal meeting," Vandroff said. "I was going over the briefing that I'm supposed to give in a month or so."
When the shooting began, he and eight colleagues barricaded the door to their conference room with chairs and tables. As they lay on the floor, he said, two shots pierced the top of the wall.
Eventually, police found them and rushed them out, hands over heads. Only later did Vandroff learn that a friend had been killed.
"Someone that I was friends with and have been friends with for a while," said Vandroff, who has been in the Navy nearly 25 years and works in procuring destroyers. "I lost a friend."
Jirus was in his tan uniform, ribbons on his chest, as he spoke hours later.
"In the Navy, we're trained for combat operations away from here. We're the 'away' team. We go off and fight other wars in other locations," he said. "So seeing someone die in front of you here where you work at is a relationship of you talking to God or you realizing just how fragile life is and how random it is, and how quickly you are here and you're not."
A 25-year veteran, Jirus works at Naval Sea Systems Command - NAVSEA, which buys, builds, and maintains ships.
When he first heard the noise on the fourth floor of Building 197, he said, it sounded like a pop gun. But when alarms went off, he went to an alley and helped direct people to safety.
There, a man - he says he thinks a civilian who worked nearby - ran up asking questions.
"He said, 'I heard there's a shooter in your building.' I said, 'That's news to me,' and that was the extent of our conversation. And then I heard two shots. And he got hit," Jirus said.
Jirus ran, leaped a fence, and met up with others who had fled.
"I've seen dead people before. That's not a shocker to me," Jirus said. "But to hear the gunshots and realize you were that close, it makes me a little unnerved. It makes me like life a lot today - hug my kids next time I see them."
He added, "I feel horrible because I have no idea who the man is."
A reporter asked about security at the Navy Yard.
"If you would have asked me that question 8 o'clock this morning, I would have said, 'Very secure,' " he said. "At 8:30 when I'm running for my life, it's a completely different answer."
"Common access cards" - CACs - are needed to enter, he said, and people are not supposed to bring guns in, but he said someone who wanted to could. Some employees said there were no metal detectors, and some doors accessible with CACs were unguarded.
Omar Grant, a civilian worker, was starting his day when he heard a loud sound - as if someone had dropped something.
"Then we heard three more shots, then that's when people starting leaving the building, running out of the building, getting the hell out of there," he said.
Ward, a logistics management specialist, works elsewhere in the complex but went to Building 197 to buy breakfast in the first-floor cafeteria.
That's when she heard a sound she described as "pop-pop-pop" - audible from the atrium.
"I didn't see anything, I just heard the gunshot and I just ran," she said. "The only thing I could think of was my family."
She added, "A lot of us panicked."
Some people's routines put them in harm's way. Others were kept safe by quirks of work or life.
Ben Acheampong should have been on the third floor - he said people he knew were killed - but he was across the street for a training class.
One man was overheard saying into a cellphone, "If I had gone to get breakfast today, I would have gotten shot at."
Many employees were hustled to the nearby Nationals Park baseball stadium and given boxed, self-heating meals. Nearby offices were locked down. Construction workers left their tools at the site of a planned condo building. Some were stranded, having parked inside what became a police perimeter.
The Navy Yard sits in the district's relatively quiet southeast corner, less than two miles from the Capitol and frequented mostly by federal employees. The Department of Transportation fills a sweep of modern offices.
A building surge is changing the area, spurred by the ballpark. There are high-end loft condos nearby and a sleek park on the waterfront. New restaurants are planned.
Near the Navy Yard, along the Anacostia River, it's common to hear, and then see, powerful military choppers buzzing to and from the installation.
On Monday morning, the quiet was instead broken by sirens.
Contact Jonathan Tamari at email@example.com or follow on Twitter @JonathanTamari. Read his blog, "Capitol Inq," at www.inquirer.com/CapitolInq.