On the morning of Dec. 2, Yvette Velasco got dressed up and flat-ironed her hair. It was an important day: The 27-year-old was going to receive the gold badge officially recognizing her as a San Bernardino County Department of Public Health inspector at a holiday work event.

The world now knows what happened: Co-worker Syed Farook and his wife Tashfeen Malik stormed into the gathering, opening fire on his colleagues. Velasco and 13 others were killed in what the FBI is investigating as an act of terrorism.

On Thursday — one week and a day after the massacre — Velasco will be remembered in an outdoor funeral ceremony, at a spot on a hill chosen by her three older sisters and parents in remembrance of her love of nature. The ceremony will mark the start of a grim procession expected to take place throughout Southern California over the next week: About a dozen memorial services, funerals and burials for those killed in the attack.

"She was more than our sister," Velasco's sister Erica Porteous, 37, said, choking up. "She was our soul mate."

For the tight-knit Velasco family, the last week has felt like "a living nightmare," Porteous said. Velasco was the baby in the family, the one her sisters all remember excitedly bringing home from the hospital and watching grow up. None of them knew she was expecting to be at the Inland Regional Center that morning. She didn't like to call attention to herself, and only mentioned a badge ceremony casually to her mother, her sisters said.

The only hint they had she was at a work gathering came from a Snapchat she sent her sister Adriana Velasco, 38. The message had a photo of her hand wrapped around a Starbucks cup and a few words mentioning a holiday party.

"Lucky," Adriana Velasco replied.

Less than an hour later, Yvette Velasco's relatives started hearing reports of a shooting in San Bernardino. Genevieve Tovar, 32, sent her sisters and parents a message telling them to be careful. The shooters were still on the loose. Porteous turned on the television and realized the building under siege was often used for county meetings. She sent a text message to a friend, asking if she knew which department was gathering there that day.

The reply sparked concern: Environmental health.

Velasco had just recently passed the exam to become a state registered environmental health specialist. She'd spent the last five years working her way up at the San Bernardino County Department of Public Health, starting off in vector control, collecting mosquitoes hovering near backyard pools and dirty puddles for disease testing, and eventually becoming an environmental health specialist, a job that sent her around the county inspecting restaurants.

It was a job she was passionate about: Even at home, she'd chide her sisters when they left out food for too long.

When the family learned it was Velasco's department meeting at the Inland Regional Center and that she'd sent a Snapchat from a holiday party that morning, they began to panic. Her father and a brother-in-law went to every hospital receiving shooting victims. Her sisters called every hospital in the region. The next morning, Velasco's father, a retired California Highway Patrol lieutenant, called his daughters upstairs and told them to pray.

"We ask God to give us the strength to face whatever is in store for us," he said.

The week that has followed has brought days of shock and a list of somber preparations they didn't ever imagine taking for a little sister: Making funeral arrangements and picking photos of a smiling Velasco at birthdays and weddings for a reception slideshow.

"Sometimes I don't even feel like getting up," Porteous said. "I still can't fully accept it."

More details have come to light about who killed Velasco and her co-workers. FBI Director James Comey said Wednesday Farook and Malik had embraced radical Islamic ideology for at least two years. What exactly motivated them and why they chose to open fire on a work event remains under investigation.

Velasco's sisters feel certain they know what she would want in the attack's aftermath.

"She would want to promote peace," Tovar said.

Velasco's parents and sisters met Thursday with the FBI and county officials.

They gave her family the badge she'd been waiting to receive.