Two women and a 4-year-old girl were killed and two other children were wounded in a shooting Monday night in a Baldwin Park neighborhood, police said.
The slayings occurred after a man argued with his mother and then shot her with a handgun, said Lt. Daniel Rosenberg of the Los Angeles County Sheriff's Department. The gunman then went next door and shot the other victims.
The two wounded children were described as a 14-year-old boy and a 9-year-old girl. She was listed in critical condition, Rosenberg said.
Police detained a man who was found standing in the street holding a handgun, Rosenberg said. Authorities did not identify him.
The gunfire broke out about 7:30 p.m.
Capt. Mike Taylor of the Baldwin Park Police Department said investigators declined to release the names and ages of the two slain women, or the names of the three children. The wounded children were taken to a hospital, said a deputy with the Sheriff's Department, which is assisting in the investigation.
The shooting scene, near North Park High School, was blocked off by yellow crime scene tape Monday night. Police cruisers and unmarked detective units stood by as the bodies of the victims and the weapon used in the killings remained at the scene.
Residents said the neighborhood, about 20 miles east of Los Angeles, was generally safe and home to many families whose children play in their frontyards.
"It's usually pretty quiet here," said Kim Thompson, 52, as she watched police move around the crime scene.