A Westchester dad fatally gunned down his wife and teen daughter and then killed himself inside their mansion Friday morning, police sources said.

The bodies of New York City property manager Steven Dym, 56, Loretta, 50, and Caroline, 18, were discovered by their cleaning lady on the second floor of their tony Fox Hill Road home in leafy Pound Ridge at around 11 a.m., police sources said.

Authorities did not say where the bodies were found or in what order the mom and daughter were killed.

A motive for the bloodbath was not immediately known, but the Dyms have a family history of violent episodes.

In 1992, Steven Dym’s mom, Paula, attacked his dad, Lawrence, with a hatchet while he slept, according to LoHud.com.

Lawrence survived and Paula was hospitalized for psychiatric evaluation, the site reports.

Steven went on to become CEO of Gabriel Management in New York City — a real-estate company founded by his dad.

The family’s own house — a 4,551-square-foot home with five bedrooms, 4¹/₂ bathrooms and a giant backyard with a pool, pergola and pond — is on the market for $1.7 million.

Loretta was a vice president of Club Quarters Hotels in Manhattan. She also volunteered for the Make-A-Wish foundation

Their daughter, Caroline, was a talented student-athlete at Sacred Heart Greenwich.

She was a star of the school’s golf team, won an award for a student film she worked on, and placed second in a regional science fair in February.

The family also has a 20-year-old son, William, who was away at the University of Southern California at the time of the murders.

The Dyms were donors during Andrew Cuomo’s failed gubernatorial run in 2002 — and he thanked the couple for their support in his 2003 book “Crossroads: The Future of American Politics.”

They were among the “extended family” listed in the book. The pair donated a combined $4,150 to that campaign, records show. They did not contribute to any of his later endeavors.

“The acknowledgements in the book were to thank many past supporters from the 2002 campaign. The governor has not seen or heard of this person in 15 years,” said spokesman Richard Azzopardi.

State Police are investigating.