BOISE -- The Idaho state fire marshal says propane from an abandoned line pooled behind a fireplace caused a tragic house fire in Donnelly that killed four people on June 30.

Knute Sandahl says the occupants renting the property were unaware it had been converted to a wood burning fireplace and weren't able to smell the propane, which had most likely been pooling for several minutes before the explosion.

The home was built in 2006 with four propane fireplace inserts. Sandahl says in 2013, the propane insert on the main floor was converted to a solid wood burning insert. The home was foreclosed in 2017. That same time the residence was added to the rental market.

The fire marshal says the original propane valve was left in place and connected to the underground propane tank, which still fueled the three other fireplaces and appliances.

"It's likely when the fireplaces were changed out, the propane fuel lines were left in place. When the Smith party arrived, they attempted to light this fireplace by turning on the valve controlling the propane. This allowed propane to free flow into the void area or concealed area behind the fireplace. It eventually came in contact with the paper that was burning in the fireplace. An explosion occurred and caused catastrophic failure of the stone fireplace itself," said Sandahl in Thursday's news conference.

The explosion blew the fireplace wall and other debris 90 feet.

William Smith was able to escape because he was far enough away from the fireplace on the other side of the room.

"Based on our findings, this office has classified this tragic event as an accident," concluded Sandahl.

"In my 22 years on the department this is the most fatalities at one specific incident that we've had, ever," said Juan Bonilla, Donnelly’s Rural Fire Protection District Chief.

Two of the victims were members of the Idaho National Guard and the other two were children.

Lt. Col. James Harper III, 49; his 14-year-old son, James "JJ" Harper; MSgt. Erin Smith, 34; and her 6-year-old daughter Autumn Smith, were killed. The sole survivor, William Smith, also a member of the Idaho National Guard and Erin’s husband, tried to save the victims.

Sandahl wouldn't comment whether the rental company or the person who built the fireplace was liable or if there would be any subsequent charges.

Tamarack Resort General Manager Brad Larsen issued the following statement Thursday afternoon:

“We are grateful for the efforts of the Fire Marshal and the fire fighters and law enforcement agencies who assisted. We are all still stunned by this tragedy, and the victims and their loved ones are never far from our thoughts.

“Based upon the conclusions of the investigation, this appears to be terrible accident resulting from an extraordinary set of circumstances. With that said, we intend to promptly share the Fire Marshal’s conclusions with all of our homeowners so they can take appropriate action if warranted.”

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