"We are extremely heartbroken for this loss", Mendocino Complex incident commander Sean Kavanaugh said, adding that officials will release more information as it becomes available.
The Ranch Fire, which achieved the dubious record of becoming the state's largest fire in its own right yesterday, remains particularly active in the northwestern portion of the fire, in the Lake Pillsbury area, where winds and fire activity picked up yesterday.
The Holy Fire was one of almost 20 blazes across California alone, which is seeing earlier, longer and more destructive wildfire seasons because of drought, warmer weather attributed to climate change and home construction deeper into forests.
The River Fire was reported to be fully contained as of Monday evening while the Ranch Fire was 59 percent contained.
Crews have been able to cut containment lines around 68% of the northern California fire, Cal Fire said.
Two other firefighters have been injured while fighting this fire. In the following days, the fire forced thousands to evacuate, and destroyed at least 18 structures within the two counties.More news: India vs England: Only thinking about making a comeback: Virat Kohli
Firefighters battling the Carr Fire further north - near Mount Shasta - did not have the same reprieve from scorching temperatures over the weekend, Jason Shanley, a Cal Fire spokesman told NPR.
It was 63% contained as of yesterday afternoon, Cal Fire said.
Monday marks three weeks since the deadly Carr Fire broke out near Whiskeytown Lake.
However, Clark denied the arson charge during a court hearing. The fire is burning near the Mendocino National Forest, about 140 miles northwest of Sacramento. The River Fire has stay the same size, at 48,920 acres, for more than a day, and containment is now 93%.
The National Park Service says Yosemite's Mariposa Grove of Giant Sequoias will reopen to the public on Monday at 9 a.m. and the Yosemite Valley on Tuesday.