A man in northern Montgomery County killed his son and daughter-in-law before turning the murder weapon on himself, according to prosecutors.

Gerald E. Mihalcik, 78, shot his son, Stephen J. Mihalcik, 56, and his son’s wife, Rebecca Hall Evans, 51, on Monday inside a home the three shared in New Hanover Township, District Attorney Kevin R. Steele said Tuesday.

"This is such a tragedy, and my heart goes out to the surviving family members,” Steele said in a statement. “We are seeing more domestic violence homicides in Montgomery County this year than ever before.”

Investigators were dispatched to the family’s home on Monday evening for reports of a shooting. Inside, they found all three victims suffering from gunshot wounds. Hall and the elder Mihalcik were pronounced dead at the scene, and medics took Stephen Mihalcik to Reading Hospital, where he died from his injuries hours later, investigators said.

It was unclear Wednesday what motivated the murder-suicide.

The incident was the latest in a string of fatal domestic violence in Montgomery County this summer.

In August, Terence W. Cheatham, 47, killed himself and his wife, Nadege St. Preux, 43, inside their apartment in Abington, police said. Weeks earlier, authorities said, Gilbert Newton III, 18, stabbed his ex-girlfriend to death during an argument outside a SEPTA station. And two days before that, Frederick J. Clea, 57, shot his wife and mother-in-law at their home in Cheltenham, according to police.

Newton and Clea were both charged with first-degree murder and related offenses.