Robin Jones, 31, who held two jobs and was an Army reservist and is remembered fondly by her neighbors in Chantilly, was listed yesterday as Fairfax County's 23rd homicide victim of the year after an autopsy.

Jones, whose body was found in the bathtub of her apartment Wednesday, died from "drowning accompanied by blunt-force trauma to the head," according to police.

There was no sign of forced entry to her one-bedroom apartment at Shenandoah Crossing, a complex of 640 apartments near Route 50 and Stringfellow Road, police said. Why anyone would kill Jones had not been determined, they said.

Jones's mother, who lives in Richmond, became worried when she hadn't heard from her daughter. She said she started making calls, and learned that Jones hadn't shown up for her job as a telecommunications assistant. Police then went to the $670-a-month apartment where Jones lived alone.

"She was always looking out for us," said Sharon Archer, her next-door neighbor. "She'd say, 'Sharon, you want something from the store?' That's how she was."

Archer said her husband saw Jones for the last time Sunday on her way to church. Jones's employer at the Giant grocery store in the Fox Mill Center, where she worked as a $7-an-hour cashier three nights a week, last saw her Sunday night.

Assistant Manager Mark T. Denhup said many of his employees are nervous after only a few weeks on the job, but Jones wasn't. "She was bubbly from the get-go," said Denhup. "She was always happy, chipper."

Denhup said Jones wanted to work as many hours as possible and was concerned about getting to the store late from her day job. He held a crumpled up piece of paper she had given him with her upcoming schedule for the Reserves.

Yesterday, Archer remembered how her friend took her 5-year-old son jogging with her, helped her through a second pregnancy, became a close friend. Archer also worried about Jones's mother, grieving back home in Richmond.

"Robin was her heart," she said.