The Montgomery County District Attorney's Office said police were called to a home in the 500 block of Privet Road in Horsham just after 7 a.m.
That's where, investigators say, the boy's father said he found his 11-year-old son dead.
Police arrived to find the child in the master bedroom where, the father said, the boy spent the night with his mother.
According to the D.A.'s office, the father told police he awoke to find the master bedroom door locked and his wife's black Toyota Highlander SUV was missing from the garage.
While police were investigating, the D.A. said officers were notified that the SUV was found partially submerged in the ocean just off Beach Avenue in Cape May, New Jersey.
"We had public works pull the vehicle out of the ocean, and once the police ran the license plate and serial number of the vehicle found out the vehicle was wanted in Montgomery County," said Cape May City Manager Mike Voll.
The mother was found by police in Wildwood Crest, New Jersey a short time later, the D.A.'s office said. She is being questioned by detectives.
The cause of the child's death is pending an autopsy by the coroner's office.
No charges have been filed at this time.
We spoke with people who live nearby in Horsham who say the woman found by police in Wildwood Crest has lived in this part of Montgomery County for decades, and always seemed like a decent person.
"She was very nice. She would see our trash can out there and she would bring it up for us when we were away," said Diane Smith.
"It's devastating, really, for the family. It's just a shame, you know, kind of heartbreaking," said Paul Howieson.