The mother, Philomena Brown, is being questioned by police but has not yet been arrested, Redwood City police Sgt. Sean Hart said.
Officers responded to the family's home at 1010 Vera Ave. at about 5:30 a.m. on reports of an assault. Brown's 23-year-old daughter and 13-year-old son were found injured and taken to Stanford Hospital.
The daughter had a skull fracture and it appeared she had been struck in the head with something, though Hart said he didn't know with what.
The son complained of pain but has since been released from the hospital, Hart said.
A next-door neighbor, Chuck Madere, said the Brown family has lived in the home for about 18 years and that he was surprised by this morning's events.
The family, along with Brown's husband John Brown, had had a Father's Day barbecue Sunday night and Madere said he hadn't heard any arguing.
One of the first signs that something was wrong was when Madere noticed Philomena Brown's car missing from her home after authorities arrived early this morning.
He said she normally leaves the house at 8 a.m. to take her son to school before heading to her job at Sequoia Hospital in Redwood City, where her daughter also works.
Madere said that when the son and daughter were taken from their home and into the ambulance, they seemed incoherent.
John Brown was taken to a hospital for observation but wasn't injured, Hart said.
Philomena Brown was found at Pompanio State Beach near Half Moon Bay this afternoon. San Mateo County sheriff's deputies spotted her car in the beach's parking lot and found her at the beach at about 2 p.m. She was taken to a hospital and placed on psychiatric hold, San Mateo County sheriff's Lt. Ray Lunny said.
Hart said she will be arrested though it is not yet clear whether she will be charged with attempted murder.
Madere said this morning's events were very out of the ordinary. "They are just a regular, hardworking family," he said.