A father of three appears to have killed his wife and his children, then taken his own life and set fire to the family home in rural western Massachusetts, the area's top prosecutor said.

Luke Karpinski and Justine Wilbur, both 41, along with their 7-year-old twins and a 3-year-old child, were found dead in their Sheffield home after the Wednesday morning fire was extinguished.

"We are investigating this matter as a murder-suicide. At this time, the evidence indicates that Luke Karpinski was the assailant," Berkshire District Attorney Andrea Harrington said Thursday.

Wilbur's body was found on the first floor of the year-old home. Karpinski and the children were found on the second floor.

The investigation is ongoing, and Harrington did not disclose how the victims died or a possible motive. The state medical examiner's office is conducting autopsies.

Karpinski and Wilbur were high school sweethearts who started dating their senior year at Wahconah Regional High School in nearby Dalton, family members told The Berkshire Eagle .

They were both attorneys who lived in Virginia before moving back to Massachusetts.

Wilbur was a patent attorney who worked in the Albany, New York, office of Hoffman Warnick and had worked on patents for cancer treatment, nanotechnology and advanced materials, the firm said in a statement.

"Justine was smart, knowledgeable, dedicated and hardworking. She was a devoted mother to her wonderful children, and a true friend to everyone in our firm," the statement said.

Karpinski was a federal chemical patent examiner who worked from home, Justine Wilbur's sister said.

The deaths were the second tragedy to hit the town of about 3,200 residents about 120 miles (190 kilometers) west of Boston in less than a week. Samya Stumo, 24, who died in the Ethiopian Airlines crash Sunday, grew up in Sheffield.