Authorities in Yosemite National Forest were trying to determine why a large tree limb fell early Friday, killing two children sleeping in their tents.
Park officials released few details about the accident, which occurred about 5 a.m. in the Upper Pines Campground in Yosemite Valley.
But witnesses described a grim scene at the campgrounds when the branch fell.
“I heard this loud bang and then a woman screaming at the top of her lungs,” camper Daniel Moore, told the San Francisco Chronicle. “I knew something was not right. I stepped outside to see what was going on and saw a lot of people clustered around their campground.