After 19 elite firefighters from Prescott, Ariz., died in a wildfire Sunday, fire officials and veterans are still unsure what went wrong:

The investigation into the events that killed more firefighters than any incident since the Sept. 11, 2001, attacks has only just begun, and many fire professionals here are reluctant to speculate about what might have happened. But those who knew the Granite Mountain Hotshots, noting their superior physical conditioning and extensive training, and the ferocity of the blaze they were battling, said they believe the result may turn out to be, as some authorities have suggested, a sudden shift in the wind or something similar.

One of the few predictable things about wildfires, they said, is their unpredictability.

“The difference between a structure fire and wildland fire is that the wildland fire will come get you, as we found out in a terrible, terrible way the other day,” said Don Devendorf, another division chief with the Prescott Fire Department.

Only one Hotshot survived the blaze. Brendan McDonough, 21, escaped injury because he was serving as a lookout about a mile from where the rest of the crew was overrun, said Wade Ward, a spokesman for the Prescott Fire Department.

McDonough realized that a wind shift had made his position too dangerous and radioed that he was moving to safer ground, Ward said. His position was soon overrun by fire.

McDonough is “distraught,” “very emotional” and “confused” about why events unfolded as they did, Ward said.

Lenny Bernstein

The city mourned the dead firefighters Monday:

At midday, Prescott officials released the names of the victims, ranging in age from 21 to 43, including Billy Warneke, 25, whose wife is pregnant; Kevin Woyjeck, 21, who followed in his father’s footsteps to become a firefighter; and Andrew Ashcraft, 29, whose wife, Juliann, learned that he was dead while watching television with their children.

Prescott was in shock. Some of the firefighters’ vehicles remained parked near the fire station. Residents came and went all day, leaving tiny stuffed dogs, water bottles and American flags in groups of 19, along with the word “heroes” in large block letters, on a hastily assembled memorial along a fence.

Later Monday, more than 1,000 people gathered in the gymnasium of Embry-Riddle Aeronautical University to remember the firefighters. Some wept as the names and ages of the dead were flashed on a screen. There was a standing ovation for the firefighters in attendance.

All the while, the 8,000-acre fire continued to burn 30 miles away in Yarnell. City fire officials said the blaze that caused the deadliest firefighting disaster in Arizona’s history was “zero percent contained.”

Each family of a victim is being assisted by a liaison “not only in their grief, but also in the process of moving on,” said Wade Ward, a fire department spokesman. Meanwhile, a task force of investigators arrived to determine what happened, hoping to release preliminary results in three days. A formal memorial service is expected Wednesday.

“Prescott is sad today, sir,” said Bonnie Winters, who works with the mother of one of the dead firefighters. “It’s really hard,” she said, her eyes filling with tears. “I was out and about today, and besides the weather being so gray, so are people’s hearts.”

Lenny Bernstein and Darryl Fears

For more on the Granite Mountain Hotshots, continue reading here.

Around the country, a range of factors is contributing to larger and more dangerous wildfires:

“On average, wildfires burn twice as many acres each year as compared to 40 years ago. Last year, the fires were massive in size, coinciding with increased temperatures and early snow melt in the West,” U.S. Forest Service Chief Tom Tidwelltold lawmakers on Capitol Hill last month, adding, “The last two decades have seen fires that are extraordinary in their size, intensity and impacts.”

Opinions differ on the precise reasons for the phenomenon. But broad agreement exists that climate change, economic development, and state and federal policies on fire prevention have played a significant role in shaping the fires raging across Western landscapes. . .

Figures from the Idaho-based National Interagency Fire Center show that federal spending on firefighting has risen dramatically over the past two decades. In 1993, the data show, federal agencies spent about $240 million fighting fires on nearly 1.8 million acres of land. Last year, the government spent nearly 10 times as much, about $1.9 billion, to combat fires on about 9.3 millionacres.

In addition, NIFC research shows that of the largest documented wildfires in U.S. history, most took place either before the early 1900s, when the government settled on a policy to fight all wildfires, or in the past two decades.

The trend seems unlikely to change anytime soon. The Quadrennial Fire Review, a wildfire crystal ball of sorts that comes out every four years, predicted in 2009 that the effects of climate change would lead to “greater probability of longer and bigger fire seasons, in more regions in the nation” — in particular, shorter, wetter winters coupled with warmer, drier summers. The report also foresaw strained fire agency budget resources at all levels – federal, tribal, state and local.

Brady Dennis and Meeri Kim

For images from Prescott, see the gallery below.