The Guard aims to protect Utahns, Tarbet said, not put them in danger.
"We failed in that [Sunday]." he said.
The Guard is prepared to take financial responsibility for the Machine Gun Fire. When asked what he would say to those who lost their homes because of the fire, Tarbet said, "We say we're sorry. We're very sorry."
Live-fire exercises at the base are on hold while the Guard investigates what went wrong.
"It's a systemic failure on our part," Tarbet said. "We're going to fix it now."
The fire began when a machine-gun round likely struck a rock on the base about 12:30 p.m. Sunday. Camp Williams fire crews which often deal with lightning-caused fires on the base thought they had the 5-acre fire under control.
But when the wind picked up, the fire exploded up the hillside.
"In our memory we've never seen a fire move that quickly," Tarbet said.
When crews realized the fire had outgrown their capabilities, they called for backup from the Unified Fire Authority.
The wind carried the flames into the brush and across several fire breaks set up to contain it, racing toward homes in Herriman. Along the way, the blaze swallowed 3,500 acres.
It was about 25 percent contained as of 8 p.m. Monday, said U.S. Forest spokesman Scott Bushman.
Nearly 5,000 residents were evacuated, and ultimately three homes were destroyed and another damaged, Unified Fire Authority spokesman Michael Bohling said. There were no serious injuries reported.
About 100 firefighters from several agencies tended to the fire overnight, in addition to about 120 Utah National Guard members and about 100 police officers from various agencies, Herriman officials said.
Another 140 firefighters are expected to arrive. Officials said the fire could be contained or extinguished as soon as today.
Bushman said crews will resume an aggressive attack on the fire beginning at 6 a.m. today, in advance of high winds expected in the afternoon that could feed the fire.
Most of the people evacuated won't be allowed to return to their homes before this afternoon, Bushman said.
"We thought [Monday] morning we'd have a lot more damage than we're finding today," said Gov. Gary Herbert, who surveyed the fire from the air as day broke Monday.
While he expected to see 25 to 100 homes lost to the flames, Herbert said the area is lucky to lose just three homes.
"It's just remarkable. In fact, it's a miracle," he said.
There were 1,652 homes and about 5,000 people evacuated as the fire spread Sunday. The homes lost in the fire were just south of Butterfield Park, said Unified Fire Authority Chief Michael Jensen. All those affected have been notified, Jensen said.
Just before 2 p.m. Monday, officials reopened a portion of the evacuation zone: areas south of 14200 South between 5600 West and Buck Brush.
Jensen said crews were still focusing on the active flames on the eastern flank, in the Rose Crest area. Fire was still smoldering in Rose Canyon on the western flank, and the National Guard was fighting flames at Camp Williams.
Rep. Jason Chaffetz and state Rep. Carl Wimmer, of Herriman, toured the area from the air Monday morning.
"From the federal side of it, we have assets that are being brought to bear," Chaffetz said. "This is going to be one of the most costly fires we've had, but the federal government is going to step up."
The Federal Emergency Management Administration has committed to pay 75 percent of the containment costs.
Tarbet called the fire an extraordinary event. He said though fires are fairly common on the training range, crews can't always go to the area because of the danger of unexploded ordnance. That leaves firefighters waiting for the fire to reach the edge of the base, where they can fight it.
But had protocol been followed, Tarbet said, staff would have known it was a red-flag day and the fire would never have started.
"We checked, but we checked too late."
On Monday evening in Rose Canyon, firefighters from Lehi, Sandy and the Unified Fire Authority were in burned areas trying to ensure smoldering brush and logs didn't reignite.
Lehi fire Capt. Kim Beck sprayed a fire hose on the smoking mass on a steep slope with rocks and remnants of burnt cactus and scrub oak.
"You've always got to be paying attention to what the fire is doing," he said.
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