[VIDEO] 19 firefighters killed by Yarnell Hill fire is Arizona's worst YARNELL, Ariz., July 1 (UPI) -- Arizona experienced its worst wildfire firefighters tragedy ever Sunday when 19 firefighters died battling the Yarnell Hill fire, officials said. State forestry officials confirmed the deaths as the uncontrolled inferno burned half the homes in Yarnell, a town of about 650 people, and blackened more than 2,000 acres, The Arizona Republic reported. "It's a dark day," Arizona State Forestry Division spokesman Mike Reichling said. He said the fallen firefighters were found in a spot where 19 fire shelters were deployed. Some were inside their shelters, which typically are used as a last resort when firefighters are overtaken by flames, and others were found outside the shelters. Eighteen of those killed were members of the Granite Mountain Hotshots team from Prescott. It wasn't known what crew the 19th firefighter belonged to, the newspaper said. "They were up there doing what they normally do," Reichling said. "It's a terrible tragedy," said Roxie Glover, director of community relations at Wickenburg Community Hospital. Reichling said federal authorities were to arrive Monday morning and state officials would begin investigating the deaths. About 400 personnel will be working the fast-moving fire, which was triggered by lightning Friday evening and had burned 200-250 structures, he said. The newspaper said Wickenburg Community Hospital was treating residents for minor injuries and smoke inhalation. State House Speaker Andy Tobin, R-Paulden, said Yavapai County Sheriff's Department officer Scott Mascher told him, "the fire took an incredibly swift turn" and it was "very, very bad." "Tonight, we need all of Arizona's prayers," Tobin said.