A veteran Mesa firefighter died while on-duty Tuesday.

When Keller's crew was dispatched to a call, he did not show up at the rig.

They found Keller, 59, deceased on the floor.

"We ask everyone to keep the Keller family in their thoughts today and support each other as we navigate this loss," the department said.

United Mesa Fire Fighters Local posted: "A true legend in the fire service has left us."

Posted on Facebook, Joleen Stonebraker Stratton shared: "This breaks my heart. We met him last summer when he responded to our 911 call when my son was choking on food. He was the nicest person. At the hospital he invited us to come see him at the fire station that coming weekend. We went there and he gave us a tour. We were so grateful for his help on one of our scariest days."