A love triangle apparently led an estranged husband to open fire on his wife's family leaving three people dead, including the shooter, police said Thursday.
Authorities have refused to release the identities of the victims pending completion of autopsies.
A wounded survivor, Jose Chinchilla, 28, was in stable condition at San Mateo General Hospital.
The police statement said the estranged husband and his wife separated in December and she began a relationship with his cousin, who was living with her. On Wednesday afternoon, the husband went to the house, argued with his wife, then produced a gun and began shooting.
A woman called 911 from the house to report "someone's going nuts," and shots were heard over the phone.
Chinchilla, the wife's brother, escaped and also called police.
When officers entered the house after failing to make contact, they found the estranged husband, the wife and another man dead.
The couple's 14-month-old daughter was unhurt, police said.