Police said officers entered the home after finding the door ajar and getting no response. They found the bodies of Linda VanDerLinden and her two sons in separate bedrooms.
Van Buren Township police Capt. Gregory Laurain said an autopsy showed Linda VanDerLinden, 34, died of strangulation but had been stabbed in the chest.
The medical examiner's report said Julien VanDerLinden, 7, and his brother Matthew VanDerLinden, 4, were stabbed multiple times in the chest and arms, Laurain said.
He said investigators believe an 8?-inch butcher knife found in the kitchen sink was the weapon used in the stabbings.
Officers went to the home on Thursday to tell Linda VanDerLinden that her husband, Michael VanDerLinden, had died in a crash in Indiana. They are now looking at whether Michael VanderLinden killed his family and then committed suicide by driving the wrong way on an interstate, instantly killing a stranger as he slammed into the man's car.
Michael VanDerLinden is "absolutely" suspected of killing his family, Laurain said. But he added, "We're following up on the leads. While the husband, Michael, is suspected of being responsible for the killings, we have not reached any conclusion, and our investigation is still continuing."
An evidence technician went through Michael VanDerLinden's vehicle after the crash but didn't find anything valuable as evidence, Laurain said. Both cars burst into flames after the collision.