A radio transmission has captured the moment 19 firefighters had their escape route cut off.
All 19 members of the Granite Mountain Hotshots died after they were overcome by flames in Arizona earlier this year.
Footage from a firefighter's helmet camera has revealed the final moments, according to a report in the Daily Mail this morning.
Firefighters could be heard pleading for water tankers to attack the blaze that had surrounded them.
"I'm here with Granite Mountain Hotshots, our escape route has been cut off," group leader Eric Marsh tells supervisors over the radio. "We are preparing a deployment site and we are burned out around ourselves in the brush and I'll give you a call when we are under the shelters."
A video of the transmission was released this week by the Arizona Forestry Division.
It also revealed that the fire commanders overseeing the Yarnell Hill Fire didn't realise the Hotshots were still battling the massive blaze.
The firefighters, from the Prescott, Arizona, Fire Department, were killed after the inferno overtook them as they huddled in their fire shelters.
The Daily Mail reports that experts say that at the time of the transmission is was likely the 19 firefighters knew they were going to die.
Jim Furnish, a retired US Forest Service deputy chief, told theArizona Republic that the sobriety of the last transmission was "quite telling".
"They knew. They knew that this was the end. They had to get in their shelters - that was the last gasp," he said.