Nineteen firefighters have been killed battling wildfires in central Arizona near the town of Yarnell.

All 19 were part of an elite “hot shot” crew, a group of firefighters who hike miles into the wilderness to clear vegetation and dig trenches to halt a wildfire’s advance.

At a news conference Sunday, Prescott Fire Chief Don Fraijo confirmed that the crew was part of the Prescott, Ariz. Fire Department. “We grieve for the family,” he said, “We grieve for the department. We grieve for the city. We’re devastated. We just lost 19 of the finest people you’ll ever meet.”

The fire originated with a lightning strike on Friday and had spread to 2,000 acres by Sunday. The area has been experiencing gusty, dry, and exceptionally warm weather. Over 50 homes have been evacuated, and, on Sunday afternoon, the Yavapai County Sheriff’s Office order the evacuation of many residents of Yarnell, a small community 85 miles northwest of Phoenix.

The 19 firefighters had been forced to deploy emergency fire “shelters,” essentially fire-resistant blankets meant to protect them from the blaze. According to Fraijo, the shelters are “one of the last fail safe methods that a firefighter can do. [The firefighters] literally . . . dig as much as they can down and cover themselves with a protective — kinda looks like a foil type — fire-resistant material — with the desire, the hope at least, is that the fire will burn over the top of them and they can survive it.”

Fraijo went on to say that the emergency shelters may only offer a 50% chance of survival and that they represent “an extreme measure that’s taken under the absolute worst conditions.”

This event is perhaps the deadliest such incident on record. In 1994, 14 firefighters were killed in a single event in Colorado. The 1954 “Rattlesnake” blaze in Southern California killed 15, and the 1949 Man Gulch fire in Montana killed 13.

Prescott is one of the only towns in the US to have a hotshot team. The unit was founded in 2002, and the city has 75 suppression team members.