The FAA and NTSB are investigating the Precision Helicopters crash that killed two pilots battling the Dome Fire wildfire in Yosemite National Park. So far, the cause of the crash is a mystery.
https://www.foxnews.com/travel/deadly-helicopter-crash-kills-2-pilots-battling-raging-wildfire-yosemite
https://www.foxnews.com/travel/deadly-helicopter-crash-kills-2-pilots-battling-raging-wildfire-yosemite