The San Bernardino County Coroner's Office said the victims were Ramon Miranda, 38, Silvia Miranda, 34, Rayna Miranda, 10 and Ramon Miranda Jr., 12, KNBC-TV, Los Angeles, reported. Relatives told the TV station the four were the parents and their children, who apparently died Monday night.
City police Sgt. Doug Imhof said the bodies were discovered by a 16-year-old boy who said his family members had been injured or possibly killed in the house.
"I'm heartbroken," neighbor Amy Harris said. "To see the look on his face. ... He's being brave, right now, but I know that it's really affecting him."
Police said the children and mother all were shot more than once, while Ramon Miranda had a single gunshot wound to the head.
Imhof said officers found blood in different areas of the house, along with "a couple of weapons," KABC-TV, Los Angeles, reported.
Neighbors told reporters arguing had been heard coming from the house earlier.