The 19 firefighters who died battling a massive, fast-moving wildfire in Arizona used tent-like shelters as a last resort once they realized they'd be caught in the blaze.
The firefighters were part of an elite crew of "hot shots" who are specifically trained to tame wildfires on the ground and contain their growth. They carry special gear including shelters that can withstand temperatures up to 500 degrees Fahrenheit, according to NBC News.
These tents are the last line of protection when firefighters are trapped in a blaze. Once flames engulf the shelters, they can burn.
Firefighters are trained to avoid situations in which they'd be trapped in a fire, but the wildfire the dead hot shot crew was battling on Sunday was especially fast-moving and unpredictable.
Incident Commander Mike Reichling told local news station ABC 15:
This fire was very radical in its behavior, the fuels were very dry, the relative humidity was low, the wind was coming out of the south, it turned around on us because of monsoon action this afternoon. That’s what caused the deaths, the change in the radical behavior of the burning fuels.
A veteran firefighter told NBC News that reports cited winds that shifted 180 degrees, which could have pushed the fire right up against the firefighters.
A spokesman for the Prescott Fire Department in Arizona called it a "perfect storm" of hazards.
SEE ALSO: Deadly Arizona Wildfire Is Just Getting Bigger [PHOTOS]