"Deputies heard gunshots followed by silence and an open phone line," he said.
Investigators combed the neighborhood Thursday outside the three-story house with a tennis court, pool and four-car garage. Investigators examined the opening mechanism of the driveway's black iron gates, and later a repairman worked on the gates.
The victim was identified as Hsiao Hsu, 45, said Sheriff's Department spokesman Ed Hernandez.
Sheriff's deputies responding to the call entered the home and found the victim. She was pronounced dead at the scene. One or more males were reported seen running away from the house, the Sheriff's Department said.
The San Gabriel Valley Tribune carried a report describing a man who came to the scene about an hour after the shooting and asked deputies, "Is my wife OK? Did you find the guy?"
The man collapsed and cried out, "No! No! No! She just called me, you lie," the newspaper said. A patrol car drove the man away.
A KABC-TV report showed an investigator in the neighborhood examining what appeared to be a handgun under a shrub.
The house is east of Los Angeles in an unincorporated area where many homes stand well back from roads, with tall hedges and gates. Horses stood quietly in a corral at one neighborhood home Thursday.
A neighbor said a couple recently occupied the home, described on real estate Web sites as being nearly 6,000 square feet and having recently sold for more than $2 million.
"They moved in only about six months ago. I've only seen them drive in and out," said Ronald Wheeler, 57, who lives across the street.
Irene and Jesus Marquez, who live nearby, said the family has two children.
"They were really nice, good people," said Irene Marquez.