A fourth firefighter died on Friday from injuries sustained while responding to the Knowles Fire on June 27.

Nathan Matthews, 43, passed away on Friday, July 24. According to a press release from the U.S. Department of the Interior, Matthews was assigned to the Rifle Helitack crew and was one of five firefighters who were involved in a burnover while working on initial attack operations on the Knowles Fire, which later merged with the Snyder Fire.

Three firefighters, Emily Barker, 38, of Clinton Township, Michigan, Nick Hutcherson, 27, of Glendale, Arizona and Sydney Watson, 27, of Warrior, Alabama, died at the scene.

“This is another heartbreaking loss for our wildland fire family,” said U.S. Wildland Fire Service Chief Brian Fennessy in the press release. “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. 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.”

A serious accident investigation team is still reviewing the circumstances surrounding the incident.

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