According to this
article , the Rim fire was started by a hunter.
"The massive Rim Fire on the west edge of Yosemite National Park was caused by a hunter who lost control of his campfire, authorities said Thursday.
The hunter, whose name has not been released, started an illegal campfire while traveling in remote wilderness within the Stanislaus National Forest, about three miles east of the Sierra foothill town of Groveland, the U.S. Forest Service said."
