Authorities say a revolver was found near the four bodies, but it was not clear whether the mother or the grandmother did the shooting. The motive behind the killing may have been a custody battle between the mother and her husband.
Authorities say Elizabeth Fontaine, 38, was in the house, along with her 67-year-old mother, Bonnie Hoult, and Fontaine's daughters, 2-year-old Julia and 4-year-old Catherine. Fontaine was an Irvine attorney and used to live in Orange County until a month ago.
"All four moved to Houston, Texas, and they came back for the child-custody hearing, which was yesterday," said Orange County Sheriff's Spokesman Jim Amormino. Authorities say the custody hearing never finished. According to the department, the father was never a suspect in the incident.
The man who lives at the home where the murder-suicide took place didn't want to talk on camera Tuesday. He grabbed some belongings from the house with the help of a detective and loaded his vehicle and left Tuesday afternoon.
Neighbors say he, his wife and young son left Monday afternoon, then called authorities, worried about his friends in the house who were visiting.
Spokesman Jim Amormino of the Orange County Sheriff's Department said police believe the two children were killed first, but they are unsure which woman was the killer.
"We do not know who did the shooting," said Amormino. "Obviously one of the adult females did. It's going to require further forensic testing to determine that."
Police said it may take a few days to determine who killed whom inside the home.