The wildfire began when Dickey shot a target that contained Tannerite, an explosive substance designed to detonate when shot by a high-velocity firearm, U.S. Forest Service Special Agent Brent Robinson wrote in an affidavit filed Sept. 20 in U.S. District Court.

Tannerite is a legal compound that has been linked to wildfires in several other Western states.

Before the Sawmill Fire was over, it had burned 47,000 acres and cost $8.2 million to extinguish, with nearly 800 firefighters battling the blaze.

At the time the fire started, winds were gusting up to 40 mph and the National Weather Service had issued a fire watch, said Chuck Wunder, chief of the Green Valley Fire Department, which was first to respond to the blaze. A fire watch is a red-flag warning that “conditions are ideal for wildland fire combustion and that there is potential for rapid spread,” said Wunder in May 2017.

Dickey was held responsible for $8.2 million in restitution, but under his plea deal he agreed to pay $100,000 when he was sentenced Oct. 9 and another $120,000 in monthly installments of $500 for the next 20 years.

Dickey was also sentenced to five years probation.