The Tuolumne County Sheriff's Department received a call at 8:25 a.m. about the tree, which fell at the campfire circle outside of the dining hall. The tree hit a group of five adult staff members.
Annais Rittenberg, a member of the Camp Tawonga staff, died after being hit by the falling tree. The other four were taken to area hospitals and are doing well, according to Ken Kramarz, the camp's executive director.
Rittenberg, 21, was a student at the University of California, Santa Cruz. This was her second year at the camp. Last year, she was a counselor, and this year, she was an art teacher.
"It's really, very hard. We were so close, especially now with all the stuff with nature, she was my teacher now. She was teaching me," said Rittenberg's mother, Penny Kreitzer. "This child was a life force and it is the most terrible tragedy."
Investigators believe the tree was weak from disease. No children were hurt. The falling tree struck a PG&E power line, and repairs were under way.
"Camp Director Jamie Simon immediately engaged our own Incident Command System to ensure that our children and staff remain safe, both physically and emotionally," Kramarz said. "The campers are doing well and are participating in camp activities away from the scene."
The camp, located in a remote area of Tuolumne County, is run by an organization based in San Francisco. There are about 300 campers and 150 staff at the facility. The camp website indicates there are sessions for students in 2nd grade through 10th grade.
It was initially reported that as many as 20 people were hurt by the falling tree.
The Associated Press contributed to this report.