An intruder attacked a resident after breaking into a home in Hacienda Heights just after midnight on Saturday, officials said.
The incident happened around 12:06 a.m. in the 16000 block of Flower Glen Drive, according to the Los Angeles County Sheriff's Department.
A person broke into a house and pistol-whipped one resident before fleeing, investigators said. It's unclear whether any property was taken.
The incident remains under investigation.
Authorities provided no further details.
KTLA's Lucas DerMugrdechian contributed to this story.