HERCULES -- The FBI has stepped in to help police find the killer of a 55-year-old retired schoolteacher found stabbed to death in her Hercules home Friday night, police said.

The killing of Susie Ko, a mother of four adult children who lived on Ash Court with her husband, is the first homicide since 2010 for this quiet suburb in West Contra Costa County.

Police do not have a motive in the killing or a suspect in custody. Police continue to search for the woman's sky blue 2011 Subaru Outback with an Idaho license plate 1A1F680 that was taken from the home's garage between 7 p.m. -- the last time neighbors saw Ko alive -- and 10 p.m. Friday.

Her husband called neighbors to check on his wife after she failed to pick him up from Oakland International Airport at 11 p.m. Friday, police said.

Hercules police Officer Connie Van Putten said Ko had been stabbed. She declined to say where on the body the woman was stabbed or how many stab wounds she had when she was found by a neighbor. Her body was on the floor in the front part of the home, police said.

She also had a head injury, and there appeared to be blood on the floor next to her body, police said. Police said the murder weapon has not been recovered.

Ko's family has been working round-the-clock to spread information about the killing and the missing car on social media sites, blogs and websites. They have set up a Facebook page at http://on.fb.me/QWZEU1 and a website at http://welovesusieko.com. The website Jalopnik.com, popular with car enthusiasts, has pictures of the missing car on its site.

A vigil for Susie Ko is scheduled for 8:30 p.m. Monday on Ash Court. The public is welcome.

"We want people to pay attention and know that we need them," said the victim's daughter Diana Ko, 27, who, along with her brother Simon, 29, and sister Sophia, 24, flew in from Los Angeles over the weekend. Sandy Ko, 32, who works and lives in London, was on her way home Sunday.

Susie Ko and her husband, Kelvin Ko, 60, moved to Idaho for his job after their children were grown. They kept the house in Hercules, and Susie Ko commuted between the two states. Her husband bought her the Subaru last year so she would have a reliable and gas-efficient car, family members said.

On Sunday, family members remembered the victim as a creative spirit quick to make a joke and always juggling projects, especially in the home's front garden. Susie Ko taught school for nearly a decade at St. Patrick School in Rodeo, which her children attended.

She came to the United States from Hong Kong in 1967.

"She was one of the kindest people I've known," wrote Kristin Mitra, who identified herself as a former student, on the Facebook page. "I was shocked. I'm still trying to wrap my head around all this."

Simon Ko believes his mother may have been a target of robbery by someone who realized the house is often vacant, or that she was home alone. He asked for anyone involved in her death to surrender to police.

"I know if my mom ever felt threatened, she'd defend the house. Hopefully, they'll make a mistake and pay for what they've done," he said.

Anyone with information can call the Hercules Police Department at 510-724-1111.

Contact David DeBolt at 925-943-8048. Follow him at Twitter.com/daviddebolt. Contact Kristin J. Bender at kbender@bayareanewsgroup.com. Follow her at Twitter.com/kjbender.