About 200 more firefighters arrived to the scorching mountains, doubling the number of firefighters battling the blaze, ignited by lightning.
Many of them were wildfire specialists like the 19 fatally trapped Sunday -- a group of firefighters known as Hotshots called to face the nation's fiercest wildfires.
With no way out, the Prescott-based crew did what they were trained to do: They unfurled their foil-lined, heat-resistant tarps and rushed to cover themselves. But that last, desperate line of defense couldn't save them.
The deaths of the Granite Mountain Hotshots marked the nation's biggest loss of firefighters in a wildfire in 80 years. Only one member of the 20-person crew survived, and that was because he was moving the unit's truck at the time.
Arizona's governor called it "as dark a day as I can remember" and ordered flags flown at half-staff.
"I know that it is unbearable for many of you, but it also is unbearable for me. I know the pain that everyone is trying to overcome and deal with today," said Gov. Jan Brewer, her voice catching several times as she addressed residents at Prescott High School in the town of 40,000.
President Barack Obama called Brewer on Monday from Africa and reinforced his commitment to providing necessary federal support to battle the fire that spread to 13 square miles after destroying 50 homes. More than 200 homes were threatened in the town of 700 people.
Obama also offered his administration's help to state officials investigating the tragedy, and predicted it will force government leaders to answer broader questions about how they handle increasingly destructive and deadly wildfires.
Brewer said the blaze "exploded into a firestorm" that overran the crew.
Prescott City Councilman Len Scamardo said the wind changed directions and brought 40 to 50 mph gusts that caused the firefighters to become trapped around 3 p.m. Sunday. The blaze grew from 200 acres to about 2,000 in a matter of hours.
Southwest incident team leader Clay Templin said the crew and its commanders were following safety protocols, and it appears the fire's erratic nature simply overwhelmed them.
The Hotshot team had spent recent weeks fighting fires in New Mexico and Prescott before being called to Yarnell, entering the smoky wilderness over the weekend with backpacks, chainsaws and other heavy gear to remove brush and trees as a heat wave across the Southwest sent temperatures into the triple digits.
Prescott Fire Chief Dan Fraijo said he feared the worst when he received a call Sunday afternoon from someone assigned to the fire. "All he said was, 'We might have bad news. The entire Hotshot crew deployed their shelters,'" Fraijo said. "When we talk about deploying the shelters, that's an automatic fear, absolutely. That's a last-ditch effort to save yourself when you deploy your shelter."
Arizona Forestry Division spokesman Mike Reichling said all 19 victims had deployed their emergency shelters as they were trained to do.
As a last resort, firefighters are supposed to step into the shelters, lie face down on the ground and pull the fire-resistant fabric completely over themselves. The shelter is designed to reflect heat and trap cool, breathable air inside for a few minutes while a wildfire burns over a person.
But its success depends on firefighters being in a cleared area away from fuels and not in the direct path of a raging inferno of heat and hot gases.
The glue holding the layers of the shelter together begins to come apart at about 500 degrees, well above the 300 degrees that would almost immediately kill a person.
"It'll protect you, but only for a short amount of time. If the fire quickly burns over you, you'll probably survive that," said Prescott Fire Capt. Jeff Knotek. But "if it burns intensely for any amount of time while you're in that thing, there's nothing that's going to save you from that."
Fire officials gave no further details about the shelters being deployed. The bodies were taken to Phoenix for autopsies to determine exactly how the firefighters died.
The U.S. has 110 Hotshot crews, according to the U.S. Forest Service website. They typically have about 20 members each and go through specialized training.
Many of those killed were graduates of Prescott High, including 28-year-old Clayton Whitted, who as a firefighter would work out on the same campus where he played football for the Prescott Badgers from 2000 to 2004.
The school's football coach, Lou Beneitone, said Whitted was the type of athlete who "worked his fanny off."
"He wasn't a big kid, and many times in the game, he was overpowered by big men, and he still got after it. He knew, 'This man in front of me is a lot bigger and stronger than me,' but he'd try it and he'd smile trying it," Beneitone said.
He and Whitted had talked a few months ago about how this year's fire season could be a "rough one."
"I shook his hand, gave him a hug, and said, 'Be safe out there,'" Beneitone recalled. "He said, 'I will, Coach.'"
Hundreds of people were evacuated from the Yarnell area. In addition to the flames, downed power lines and exploding propane tanks continued to threaten what was left of the town, said fire information officer Steve Skurja. A light rain fell over the area but did little to slow the fire.
"It's a very hazardous situation right now," Skurja said.
Arizona is in the midst of a historic drought that has left large parts of the state highly flammable.
"Until we get a significant showing of the monsoons, it's showtime, and it's dangerous, really dangerous," incident commander Roy Hall said.
The National Fire Protection Association website lists the last wildfire to kill more firefighters as the 1933 Griffith Park blaze in Los Angeles, which killed 29. The biggest loss of firefighters in U.S. history was 343, killed in the 9/11 attack on New York.
In 1994, the Storm King Fire near Glenwood Springs, Colo., killed 14 firefighters who were overtaken by an explosion of flames.
More than 1,000 people turned out Monday to a gym at the Prescott campus of Embry-Riddle Aeronautical University to honor those killed.
At the end of the ceremony, dozens of wildfire fighters sporting Hotshot shirts and uniforms from other jurisdictions marched down the bleachers to the front of the auditorium, their heavy work boots drumming a march on the wooden steps.
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