SAN BERNARDINO, Calif. — Huddled beneath a desk, a bookshelf shoved against a locked office door, Regina Kuruppu held tightly to her co-workers’ hands and began to pray aloud, unable to drown out the terrifying cries coming from one story below. “Heavenly Father. Watch over my family,” she said. “Watch over us.”

When the fire alarm had sounded minutes earlier, Kuruppu was sitting at her desk on the second floor of Building 3 at the Inland Regional Center. A 19-year veteran of the organization that helps those with developmental disabilities such as autism and cerebral palsy, Kuruppu was wrapping up her pre-vacation emails, sending notes of thanks to the center’s supporters.

The alarm, she thought, was just a drill – until she got downstairs and saw two bodies in a pool of blood.

She didn’t stop to wonder what evil had come to the center that morning. Those questions would come later, for her and for a nation left grappling not only with another mass shooting, but another potential act of terrorism.

Barricaded upstairs, Kuruppu could only pray for protection – even as she prepared to die. She thought of her son. She texted her sister. They exchanged their “I love yous.”

“I’m going to leave this world,” she thought.

The Inland Regional Center serves as both a reliable employer for some 600 area residents and a haven for the tens of thousands of vulnerable clients it serves. December is an especially busy month at the center and the auditorium space on the first floor of Building 3. Kuruppu’s co-workers had spent the day Monday decking out the room for upcoming festivities.

The center’s annual holiday party for clients was Tuesday afternoon, and a winter dance complete with ugly sweater contest was scheduled three days later. In between, the auditorium had been rented to an outside client: The county’s Division of Environmental Health Services had scheduled a training session and holiday luncheon for as many as 90 employees on Wednesday.

Food inspector Chris Nwadike arrived that morning looking forward to time away from the daily grind of the Health Department, where he’d worked some 25 years. Doughnuts, tamales and downtime with co-workers awaited at an event that always mixed business with pleasure.

For Bennetta Betbadal, a fellow food inspector, the gathering was a chance to see friends. For Jennifer Stevens, who started at the agency after graduating from college in June, the luncheon was a first-time event.

As the attendees settled in, supervisors reviewed the year’s work and announced plans to hire more employees in 2016. They played a trivia game, vying for gift cards. Then came a 20-minute break before lunch.

Nwadike shared a table with restaurant inspector Syed Rizwan Farook, a quiet man employed at the agency for five years. “He’s serious with his job,” Nwadike said later. “He doesn’t play around.” It had been a big year for Farook. Co-workers threw him a shower before his daughter was born. They organized a potluck and collected cash for him and his bride of a year, Tashfeen Malik.

Regina Kuruppu and Christian Nwadike describe hiding during the shooting rampage last week at the Inland Regional Center in San Bernardino, Calif.

Christian Nwadike describes hiding during the shooting rampage last week at the Inland Regional Center in San Bernardino, Calif. The Associated Press

At the meeting, Farook slipped out before the trivia game, leaving behind belongings, as if he planned to return. By break time, he was still missing. Nwadike headed for the restroom. Environmental health specialist Denise Peraza used the time to grade papers for a class she taught. It was just before 11 a.m.

Suddenly, doors to the conference room leading to an adjacent parking lot burst open. Sunlight blazed into the room, followed by gunfire blasts. “Five rounds heard,” police dispatch recorded at 10:58 a.m. Then one minute later: “Heard about 20 to 25 rounds.”

Two figures dressed in black were firing semi-automatic rifles.

Stevens at first thought someone was playing a joke – until she got hit. “She looked down and she had a big hole in her side,” said her mother, Lisa, who recalled her phone ringing after the rampage began and hearing her daughter’s horrifying words: “Mommy, I’ve been shot.”

Peraza dove on the floor under a table, alongside co-worker Shannon Johnson, who wrapped his arm tightly around her as they tried to shield themselves with a fallen chair. “I got you,” Johnson told Peraza, who felt something hit her lower back.

Nwadike had been in the men’s room about four minutes when gunfire tore tiles off the wall, striking a colleague who sensed what was happening: “Somebody is shooting! Lie down! Lie down!”

From inside the office upstairs, Kuruppu and the three co-workers hiding with her heard the shots, the wails and then feet running down hallways. At 11:10, when SWAT member Ryan Starling arrived, people were running from the building. Other officers already were inside the auditorium, where fire sprinklers sprayed down on a sea of carnage. The water, tinged red, flowed “like a little river of blood coming out,” Starling said.

Scattered about, 21 people were wounded but alive. Stevens and Peraza were among them. Fourteen others were killed, including Bennetta Betbadal and Peraza’s hero, Shannon Johnson.

Upstairs, some 20 minutes passed before men in uniform busted down the office door and found Kuruppu and her colleagues. A day later, the woman who runs support groups for others was still trying to heal and make sense of it all.

“Fear is not what God wants us to feel,” she said. “He wants us to feel at peace.”

But peace hasn’t found San Bernardino yet.

Four hours after the rampage, police found the apparent assailants: Farook, 28, and his wife, Malik, 29, both died in a shootout with police, leaving behind their 6-month-old daughter. They were armed with assault rifles and semi-automatic handguns. Investigators would later find a cache of ammunition and pipe bombs.

The FBI said Friday that it is investigating the shooting as an act of terrorism, but the agency’s director said there is no indication that the two were part of a larger plot or members of a terror cell.

If the massacre was inspired by Islamic extremism, it would be the deadliest such attack on U.S. soil since Sept. 11, 2001.

For those who worked alongside Farook, the allegations are difficult to fathom.

“I didn’t see anything that this guy would do this type of thing,” said Nwadike, who escaped unhurt. “When I look at those that died, I know them. I’d see them almost every morning. That touches me, and then I start thinking about myself. I’m still talking.

“Right now,” he said, “I’m home.”