The Idaho State fire marshal and the Valley County coroner on Monday released new information about a tragic house fire in Donnelly that killed four people.

Fire Marshal Knute Sandahl said his office has narrowed the focus of its investigation to a propane-fueled fireplace on the main floor of the house. Because the investigation is still ongoing, a definite cause has not been determined yet.

“We're really trying to put closure for the family and be able to give them some answers of what happened," Sandahl said.

Also on Monday, the Valley County coroner identified the four victims of Friday night’s fire. Two are members of the Idaho National Guard.

Lt. Col. James Harper III, 49; his 14-year-old son, James "JJ" Harper; MSgt. Erin Smith, 34; and her daughter Autumn Smith, who is either six or seven years old were killed. The sole survivor, William Smith, also a member of the Idaho National Guard and Erin’s husband, tried to save the victims.

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"We do know that the survivor and a neighbor did attempt a rescue, but unfortunately they were driven out by the extreme heat and smoke that had quickly took over the residence," Sandahl said.

Investigators believe the victims were trapped in the burning building. Sandahl said they were found in the same room. He also said it appears a wall collapsed. The focus of the investigation is a propane fueled fire place that was located on the main floor of the house.

"Witnesses have told to us that there was a loud boom which would indicate an explosion, and some of the physical evidence that we saw and observed would certainly add credence to that report," Sandahl said

He said propane is commonly used for heating in rural parts of Idaho, and if there is a mishap, it can be explosive.

It could still be weeks before investigators have a definitive cause of the fire. The fire marshal said they still have data to collect and they’ll be working with the insurance company to gather information. Sandahl wants to be able to give everyone affected by this tragedy some answers.

"Our hearts really go out to them. This is a very tragic loss that nobody ever wants to happen in their neighborhood or community,” he said. “We're going to do everything that we possibly can to come up with some answers and add to the closure."

Also on Monday, James "JJ" Harper's mother and stepfather released the following statement:

"We are devastated at the loss of our amazing son JJ Harper and his father, our friend Jim. JJ's infectious smile, his hearty laugh, his big heart, and his leadership on the football field will be missed by everyone. JJ and Jim were apart for 2 deployments overseas in JJ's short life and they lived every minute of every day to make the time they had together count... Our hearts are also with the Smith family during this difficult time."

The family added that they will hold a memorial hike to Table Rock to honor JJ. The hike was originally set for Saturday, July 15 at 1 p.m. but has been moved to 10 a.m. A memorial service for the teen will be announced at a later date.

A GoFundMe page has been set up as a memorial fund for JJ.