LIVERMORE, Calif. — A young mother has admitted to investigators that she stabbed her 7-month-old son to death in a popular Northern California park, police said Sunday.

Ashley Newton, 23, of San Jose was arrested Saturday on suspicion of murder, the East Bay Regional Parks District Police Department said in a statement.

Investigators continue to interview her family and friends in an attempt to make sense of the alleged crime.

“This is an extremely shocking case for us,” said Chief Timothy Anderson of the park’s police department.

The motive remains unclear, but Anderson said that Newton had a history of depression and appeared to have self-inflicted knife wounds on her wrist.

Police were called at 10:30 a.m. Saturday on reports of a damaged Honda sedan in the Del Valle Regional Park east of San Francisco. They found the car abandoned with the engine running and an empty child’s seat.

Officers were about to tow the car by 12:30 p.m., believing it was involved in a hit-and-run, when Newton walked up to them holding her lifeless baby, Anderson said.