People gathered for an emotional vigil Monday night in Hercules to honor a retired school teacher who was slain in her home over the weekend.

Police said 55-year-old Susie Ko was stabbed and beaten to death in her Hercules home last Friday night.

On Monday, the last of Ko's four children arrived back in town. This was the first time since Ko was killed that her family has been back to their home on Ash Court.

The cul de sac was filled with about 200 people carrying candles for the vigil.

Friend who knew her described the long-time teacher as a mother figure to everyone she met.

"I keep expecting her to come back and say 'It's okay. I have it fixed.' It's surreal," said friend Cynthia Ip.

Earlier Monday, police had the street cordoned off with yellow tape as two Hercules crime scene investigators, assisted by a dozen FBI technicians, took truckloads of evidence to the lab.

"We were looking for a blood trail. The victim was stabbed and we have not been able to locate a weapon," said Connie Van Putten of the Hercules Police Department.

Police also want to find her car, a pale blue Subaru with Idaho plates. It was stolen the night she was killed.

The car is the only item that appeared to be missing.

Investigators have fielded a number of calls about possible sightings of the car across Northern California. Police believe Ko's killer may have changed the plates on the car, Van Putten said.

"If someone sees a sky blue Subaru Outback and it seems suspicious to them, and they can safely get a license plate, we would really appreciate the license," Van Putten said.

Ko's children returned to Hercules to support their grieving father, and to encourage the public to help find the killer of their mother.

"We are just trying to surround him with love," Simon Ko, 29, said of his father.

Simon Ko remembered his mother, who taught elementary school in nearby Rodeo for more than 13 years and lived in Hercules for more than 30 years, as a "very high spirited, social and fun-loving person."

The Ko family is using the internet to spread the word about the missing car to generate tips.

They reached out to specific industries.

"Including law enforcement, first aid ambulances, anyone whose traveled the streets," said the victim's son, Simon Ko.

The family has set up a website for tips and information at welovesusieko.com.

Keeping busy keeps this grief stricken family from thinking about the unimaginable.

"Imagine the sudden death, all the pain my wife went through. It's really horrific," said her husband Kelvin Ko.

The family said the vigil was both heartbreaking and heartwarming. Ko's children, most of whom moved away after college, said people they hadn't seen childhood came to show how much they cared.

The homicide is the first in Hercules since 2010, Van Putten said.

The mostly residential community of upscale homes and quiet neighborhoods about 23 miles northeast of San Francisco has only seen five homicides in the past 12 years, she said.

"We think we have a safe city, Van Putten said. "We've had a few robberies and some burglaries, but as far as violent crime, we just haven't had that much."