A fourth firefighter died from burn injuries battling Colorado’s Knowles wildfire in the western part of the state at the end of June.

Nathan Matthews, 43, of Lincoln, Nebraska, died from injuries sustained while battling the blaze, the U.S. Department of the Interior said in a statement. 

“This is another heartbreaking loss for our wildland fire family,” said U.S. Wildland Fire Service Chief Brian Fennessy, referring to the three firefighters who died responding to the Knowles blaze. Fast-moving flames and gusty winds created unpredictable conditions for the firefighters. 

Five firefighters were involved in a burnover — when a fire spreads rapidly and closes off escape routes — while engaged in initial attack operations on the Knowles Fire. The fire sparked near Knowles Canyon in Mesa County and was later overtaken by the Snyder Fire, which started in Utah and rapidly spread across the Colorado border.

The Department of the Interior said the fire is known as the Snyder Fire and has burned over 28,000 acres along the Colorado-Utah border. 

Emily Barker, 38, Nick Hutcherson, 27, and Sydney Watson, 27, were assigned to the Rifle Helitack crew and engaged in initial attack operations, officials said. They died at the scene. 

“We mourn the loss of Nate while continuing to grieve the deaths of Emily, Nick and Sydney. Our hearts are with their families, friends, crewmates and everyone impacted by this tragedy,” Fennessy said. 

Matthews had been receiving medical care for his burns. The name of the fifth firefighter has not been released.

“We remain committed to supporting those affected and honoring the legacy of all four firefighters who made the ultimate sacrifice in service to our nation,” Fennessy said.