HUBBARD, Ore. -- The five family members found dead in the burned rubble of a house fire in Hubbard died in a murder-suicide, the Marion County District Attorney's Office concluded.

An autopsy confirmed the three children and adult man died of a gunshot wound to the head. The adult woman died of blunt force trauma to the head. Investigators said the house fire was set intentionally.

The Oregon State Medical Examiner said the remains were the family that lived at the home: 42-year-old Keith Kroeker and 39-year-old Erin Kroeker, and their 10-year-old twin boys and a 7-year-old daughter.

The Marion County Sheriff's Office said the case was focused on murder-suicide.

"After reviewing that entire seven-month investigation, the Marion County District Attorney's Office has concluded that Keith Kroeker is solely responsible for the deaths of Erin Kroeker and their three children," said a news release from the DA's office.

At 3 a.m. on Jan. 3, crews were called to the 18000 block of Fobert Road NE and found three structures on fire, a hot power line and lack of onsite water.

Thirty minutes after arriving, firefighters found a person dead in the home and notified police. The other four bodies were found over the next two days.

Family members say the Kroekers are a wonderful, loving, Christian family and nobody knew of any marital or financial problems. Keith was a senior design engineer at Intel and Erin is a full-time mom.