A change of routine may have saved defense contractor Brendan Kittredge from a gunman’s crosshairs during Monday’s deadly shooting rampage at the Washington Navy Yard, home to some 16,000 civilian and military employees.

As a matter of routine, the 28-year-old Arlington resident normally eats breakfast at Building 197’s ground-level cafeteria, where a shooter trained much of his gunfire that morning from the fourth floor of an atrium. But Kittredge, who works for the NAVSEA naval systems command, opted instead for a cafe on the other side of the base Monday. (View an interactive map of the Navy Yard).

He ate and made his way to work, walking within 50 yards of his office complex before a man busted through the front door, yelling: “Shots fired, shots fired on the fourth floor.”

(Saul Loeb/AFP-Getty) - Police investigate a shooting at the Navy Yard on Sept. 16. (Saul Loeb/AFP-Getty) – Police investigate a shooting at the Navy Yard on Sept. 16.

Kittredge ran to a nearby building and told a security guard what he’d heard. Before he could finish, word came across the man’s radio that an active shooter was on the loose.

“He ran right out the door,” Kittredge said of the guard. “I don’t know if he had a gun drawn or what he was doing. I was trying to go in the opposite direction.”

The shooting spree continued until at least 13 people were dead and more wounded. Among the fatalities was suspect Aaron Alexis, 34, of Forth Worth, who was killed in a gun battle with police.

Kittredge hunkered down with other base workers in a room with only swipe-card access. He heard no gunfire, but the sound of sirens and helicopters kept occupants on edge as they waited behind the safety of a door they had buttressed with filing cabinets. “We were really unsure of what to do and what was going on,” Kittredge said.

Eventually, computers everywhere started beeping as a base warning system alerted employees that they should “shelter in place.” Every hour or so, a department manager would relay the status updates he picked up from conference calls with security personnel.

Employees speculated about what was happening outside. Some had been in Building 197 when the shooting started. One was on the second floor of the atrium.

“He said it sounded like someone dropped a huge conference table,” Kittredge said. “He thought someone was setting up for a party and dropped a table. Then he heard more shots and ran out.”

Kittredge had no cell reception, so he used a computer to reach his family, friends and co-workers. His father, John Kittredge, learned his son was alive through Facebook. “I’m safe, locked in another building,” the message said. “If I ever get out of here I’ll call. We might be moving buildings or something. I don’t know. Don’t want to go outside if they’re looking for another dude.”

On Monday afternoon, it was still unclear whether a lone gunman had perpetrated the deadly attack. Authorities were still looking for a second suspect, described as a black man in his 40s, with gray sideburns and wearing an olive-drab military-style uniform.

But authorities later that night expressed confidence that Alexis was the sole shooter.

“We have exhausted all means that we have available to either support or discount” eyewitness accounts of a possible second shooter, D.C. Police Chief Cathy Lanier said at a press conference. “We are comfortable we have the single and sole person responsible for the loss of life on the base today.”

Part of that certainty came from interviewing base employees before they left for home. Kittredge said they were told to remain in their hiding place until police and FBI investigators arrived. “Every single person had to talk on the way out and give information,” he said.

At about 5:30 p.m., Kittredge was finally released. He was given the day off of work for Tuesday but is unsure what will happen in subsequent days. He has no reservations about returning.

“I don’t feel any different than anyone else in the country should feel about going back to work,” Kittredge said. “I don’t think the Navy Yard is any less safe than other places. If anything, it’s more safe. It just goes to show that this type of thing can happen anywhere.”

* Julie Tate contributed to this report.

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