PRESCOTT, Ariz. (AP) -- Shortly before 19 elite firefighters perished in a raging Arizona wildfire, commanders thought the crew was in a safe place. No one had heard from the Granite Mountain Hotshots for 33 minutes. The crew didn't contact commanders, and commanders didn't radio them.
Then it was too late. (Story continues below video.)
A three-month investigation into the June 30 deaths released Saturday did not determine if the tragedy was avoidable, while outlining a series of missteps by the crew and commanders and revealing the more than half-hour of radio silence that occurred just before the firefighters were overwhelmed by flames.
It's not certain why the crew left what was believed to be a safe spot on a ridge that the fire had previously burned and, apparently seeking another safe location, unknowingly walked to their deaths in a basin thick with dry brush. At the time they died, an airtanker was circling overhead, confused about their location.
"There is much that cannot be known about the crew's decisions and actions" because of the gap in communications, the report concluded.
The 120-page report by a team of local, state and federal fire experts pointed to repeated problems with radios and contact with the crew. At one point, a pilot wanted to check on the firefighters after hearing radio traffic that they might be on the move, but commanders believed at that time the crew was positioned safely.
Ted Putnam, a former investigator for the U.S. Forest Service, said the report didn't go far enough to dissect the decisions made by the firefighters. When the crew members went silent and did not notify anyone they were changing locations "there's an active failure there," he said.
At a news conference in Prescott, where the fallen firefighters lived, Shari Turbyfill implored officials to draw stronger conclusions about why her stepson and his fellow firefighters died, and recommend immediate changes.
"I don't want another family to deal with this," she said.
Her husband, David, said the emergency fire shelter in which his 27-year-old son Travis died had not been improved in 13 years.
"Policies, as they may be, need to change," he said.
Despite identifying numerous problems, the report found that proper procedure was followed in the worst firefighting tragedy since Sept. 11, 2001. Investigators suggested that the state of Arizona should possibly update its guidelines and look into better tracking technology.
All but one member of the Granite Mountain Hotshots crew died while protecting the small former gold rush town of Yarnell, about 80 miles northwest of Phoenix, from an erratic, lightning-sparked fire. Hotshots are elite backcountry firefighters who hike deep into the brush to fight blazes.
Investigators described what became a chaotic day in which a fire that two days earlier caused little concern bloomed into an inferno that incinerated pine, juniper and scrub oak in an area that hadn't experienced a significant wildfire in nearly a half century.
The day went according to routine in the boulder-strewn mountains until the wind shifted around 4 p.m., pushing a wall of fire that had been receding from the firefighters all day back toward them. The report suggested the crew was blindsided when the fire changed direction and surged in intensity and speed.
Commanders did not find out the men were surrounded by flames and fighting for their lives until five minutes before they deployed their emergency shelters, which was more than a half hour after a stormy weather warning was issued.
Without guidance from the command center or their lookout, who had escaped after warning the crew, the men bushwhacked into a canyon that soon turned into a bowl of fire. The topography whipped up 70-foot flames that bent parallel and licked the ground, producing 2,000 degree heat. Fire shelters, always a dreaded last resort, start to melt at 1,200 degrees.
The report confirms the crew knew about the changing weather, and just before 4 p.m. a commander warns the crew superintendent to "hunker and be safe."
There was no word from the crew from just after 4 p.m. until just minutes before the fire overwhelms them -- a gap of 33 minutes.
Shortly before they deploy their shelters, a static-filled transmission comes over an air-to-ground frequency from a crew member at 4:39 p.m.: "We are in front of the flaming front."
Other firefighters working on the blaze who pick up the transmission are confused, hearing the urgency in the Hotshot's voice and chain saws roaring in the background. They believed the crew was in a safe spot.
In final snippets of conversation, the crew superintendent says urgently "our escape route has been cut off. We are preparing a deployment site" for the shelters.
He's assured an airtanker is coming.
But a smaller plane makes seven passes over four minutes trying to locate the crew to guide the big tanker, but cannot find or contact them.
Heavy smoke blankets the ground.
A helicopter joins the search but "there is no further contact with the Granite Mountain" crew, the report said.
The firefighters may have failed to communicate during that crucial half-hour because they entered a dead zone, or because they were wary of overloading the radio channels. In the end, the same communication gaps that stymied the rescue effort hindered the reconstruction of the tragedy.
"We don't know that information; we don't have it," lead investigator Jim Karels said. "That decision process went with those 19 men."
The fire destroyed more than 100 homes and burned 13 square miles before it was fully contained on July 10.
No other wildfire had claimed the lives of more firefighters in 80 years.
Blood reported from Los Angeles. Hannah Dreier in Las Vegas and Michelle Price in Salt Lake City contributed to this report.