A bullet like that has enough energy to travel several thousand feet per second, said Ward, and that energy has almost a "molten" effect on the casing. The heat from that bullet's energy — rather than a spark from it colliding with something — ignited the fire, he said.
The area where the fire began is on public land, where target shooting is legal, according to Ward. Many shooters practice in the area and leave behind litter, including items used for target practice, like refrigerators and televisions, he said.
The fire has burned mostly grass and bushes, though there was "a little bit" of timber that had also been charred, Ward said.
"It's almost 100 degrees out here. The relative humidity is low," Ward said. "Any heat source" has the potential for starting a fire.
"No one is setting fires intentionally in this area," he added, but he asked that the public be aware of the conditions before engaging in an activity that could result in a fire.
"There's a time and place for everything," he said.
On Sunday morning, residents of about two-dozen homes near the wildfire were evacuated as a precaution, but they were allowed to return home after the evacuations later that day. No one has been reported injured and no structures were being threatened as of Monday night.
Trails running through the burned area were closed, fire officials said.
With perimeters increasingly secured, the flames were moving uphill and away from residential areas toward a Uinta-Wasatch-Cache National Forest wilderness area.
Ward said crews planned to focus on using natural terrain and construction of new lines and breaks to contain the fire.
Otherwise, the blaze will be allowed to burn itself out within its interior, which Ward described as dangerous steep and rugged country for firefighters. The fire has cost about $450,000 to fight.
Twitter: @remims, @mnoblenews
Editor's note: Due to an erroneous news release, the cost of fighting the fire was misstated in an earlier version of this story.