At a time when all his energy should go to spoiling his grandsons, Larry Mendonca is doing the unthinkable. He is spending every day of his retirement trying to find their mother's killer.

It's a quest and a burden, but Mendonca knows things no father should know.

When his daughter was murdered a year ago today near her home on Kaua'i, her killer took a length of plastic cord, wrapped it around her neck and strangled her. Neighbors found Sandra Galas, a 27-year-old mother of two, left for dead in her parked car.

Doing something has helped Mendonca make sense of what happened while he waits for police to solve the only homicide on Kaua'i in 2006.

Mendonca has talked often to people who knew his daughter, has read her personal e-mail and has handed out bumper stickers that say, "Never Forget Sandy G." He's dipped into savings to fund a $10,000 reward for information that gets her killer convicted.

"I don't know if I am coping or not, but my philosophy is not how do we cope but that we have to," Mendonca said. "I have to. I will not stop until my last breath or until I have closure."

Galas was the youngest of two children and Mendonca's only daughter.

Mendonca moved his family to Kaua'i — where he was born and raised — when he retired from the U.S. Air Force in 1980. His son was 4, his daughter 2.

"Kaua'i was the ideal place to raise children," he said. "You didn't have the hustle and bustle of the big cities. You didn't normally have the big crime rates that you do in big cities. It was more rural. It was to our liking and the kids seemed to enjoy it."

After graduating from high school in 1996, his daughter majored in journalism at the University of Hawai'i-Hilo, but quit in her third year. She had been home the previous summer and met a man named Darren H. Galas. They wanted to marry.

For the first two years, the marriage was good and the couple lived in a home Mendonca gave them in Eleele Nani.

But the marriage crumbled in 2005 and Galas told her husband to move out, her father said. In August, she filed for divorce.

Sandra Galas tried to turn her life around at that point. From October until her death, she was the assistant food and beverage manager for the Grand Hyatt Resort and Spa in Po'ipu.

Kaua'i police have said little publicly about the murder, but some of them have shared details with Mendonca. As a rule they won't release the cause of death, but Mendonca has a copy of Galas' death certificate.

"She was basically strangled with a thin cord," he said. "We think it's a thin monofilament line or a Weed Eater type of line. This is what the marks on her neck showed."

Police said they arrested only one person in the days after Galas was killed — her husband — but released him after 48 hours.

Darren H. Galas, 35, did not return several calls. He lives in Lawa'i and is raising the couple's two children.

"He was brought in for questioning and not officially charged," said Kaua'i police Detective Sam Sheldon. "The investigation led that way. I won't go into details on that."

Other people also have been questioned, but there were no additional arrests, Sheldon said.

Roy Asher, acting assistant police chief, said the case is frustrating. With only one homicide to solve for 2006, he would like to find the culprit.

But having a suspect and proving guilt are often difficult to put together, he said.

"You have to have some physical evidence," he said. "Sometimes we need physical evidence and an eyewitness. We can show means and motive but that is not always enough anymore."

A lot of Mendonca's friends shook their heads after his daughter's death, doubtful that her killer would ever be caught, he said. And to a large degree, that's what drives Mendonca to remain involved.

He gathers whatever shreds of evidence that he can, convinced that his daughter's killer will make a mistake that will lead to a murder conviction.

"We want to keep this case alive for as long as it takes," Mendonca said. "You cry a little bit when you get up in the middle of the night but you don't stop. You keep going."

Reach Mike Gordon at mgordon@honoluluadvertiser.com.