YARNELL, Ariz. (AP) — As the windblown blaze suddenly swept toward them, an elite crew of firefighting “Hotshots” desperately rushed to break out their emergency shelters and take cover on the ground under the heat-resistant fabric.

By the time the flames had passed, 19 men lay dead in the nation’s biggest loss of firefighters in a wildfire in 80 years.

The tragedy Sunday evening all but wiped out the 20-member Granite Mountain Hotshots, a unit based in the small town of Prescott, Prescott Fire Chief Dan Fraijo said as the last of the bodies were retrieved from the mountain. Only one member survived, and that was because he was moving the unit’s truck at the time, authorities said.

The deaths plunged the town into mourning, and Arizona’s governor called it “as dark a day I can remember” and ordered flags flown at half-staff.

“We are heartbroken about what happened,” President Barack Obama said while on a visit to Africa. He predicted the tragedy will force government leaders to answer broader questions about how they handle increasingly destructive and deadly wildfires.

The lightning-sparked fire — which had exploded to about 13 square miles by Monday morning — destroyed about 50 homes and threatened 250 others in and around Yarnell, a town of 700 people in the mountains about 85 miles northwest of Phoenix, the Yavapai County Sheriff’s Department said.

Residents huddled in shelters and restaurants, watching their homes burn on TV as flames lit up the night sky in the forest above the town.

It was unclear exactly how the firefighters became trapped. 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.

Brian Klimowski, meteorologist in charge of the National Weather Service’s Flagstaff office, said there was a sudden increase and shift in wind around the time of the tragedy. It’s not known how powerful the winds were, but they were enough to cause the fire to grow from 200 acres to about 2,000 in a matter of hours.

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.

As a last-resort effort at survival, members are trained to dig into the ground and cover themselves with a one-man, bag-like shelter made of fire-resistant material, Fraijo said.

“It’s an extreme measure that’s taken under the absolute worst conditions,” Fraijo said. Eeven then, the shelters can be undone by heat and flame and do not always save lives.

Arizona Forestry Division spokesman Mike Reichling said all 19 victims had deployed their shelters.

The flames apparently enveloped the shelters. Autopsies were scheduled to determine how the firefighters died.

Gov. Jan Brewer’s voice caught several times as she addressed reporters and residents at Prescott High School.

“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,” she said.

On the bleachers, two women held each other and wept into tissues. An elderly man clutched a wooden walking stick and gazed at the ground. Many of the residents were red-eyed, and listened with their hands over their mouths.

A makeshift memorial of flower bouquets and American flags formed at the Prescott fire station where the crew was based. Prescott resident Keith Gustafson showed up and placed 19 water bottles in the shape of a heart.

“When I heard about this, it just hit me hard,” he said. “It hit me like a ton of bricks.”

The U.S. has 110 Hotshot crews, according to the U.S. Forest Service website. They typically have about 20 members each.

Hotshot crews go through specialized training and are sent in to battle the nation’s fiercest wildfires. Sometimes they hike for miles into the wilderness with heavy gear to build lines of protection between people and fires.

More than 200 firefighters and support personnel were assigned to the wildfire as of Monday morning. They included 18 Hotshot crews from around the country. The number of Hotshot crews assigned to the fire is expected to at least double, Reichling 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 show time 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 on 9/11 in New York.

In 1994, the Storm King Fire near Glenwood Springs, Colo., killed 14 firefighters who were overtaken by an explosion of flames.

TV aerial footage showed law enforcement vehicles patrolling Yarnell, driving down streets with burned buildings on both sides.

Among those who fled were Chuck Overmyer and his wife, Ninabill. They were helping friends leave when the blaze switched directions and moved toward his property. They loaded up what belongings they could, including three dogs and a 1930 hot rod, on a trailer.

As he looked out his rear-view mirror, he could see embers on the roof of his garage.

“We knew it was gone,” he said.

He went to the Arrowhead Bar and Grill in nearby Congress, where he and other locals watched on TV as fire destroyed his house.

The Red Cross opened two shelters in the area — one at Yavapai College in Prescott and the other in a high school gym.