Officials say a firefighter killed while battling a wildfire near Yosemite National Park was driving a bulldozer and trying to prevent the fire from spreading. Braden Varney, 36, was a second generation firefighter, state fire officials told CBS Sacramento. California Department of Forestry and Fire Protection Chief Nancy Koerperich said Saturday that Varney was cutting a "fire break" with the vehicle to prevent the blaze from spreading when he was killed. First responders haven't been able to retrieve Varney's body from inside the bulldozer because of a "rollover." Koerperich says he'd been working since the fire broke out Friday night and was making his way out of the fire area when he was fatally injured. Officials are still trying to determine the circumstances surrounding his death.