Rittenberg was an environmental studies major at the University of California, Santa Cruz, where she was a popular college DJ who served as world music director at the school's radio station, station manager Alec Howard said. The camp's executive director, Ken Kramarz, called Rittenberg a "beloved member of our staff."
"As our own hearts are still hurting, we send our sincerest condolences to her family and loved ones," Kramarz said in an email sent to campers' parents. Moore, who served as a lifeguard at the camp and ran programs at the pool, said she had only just gotten to know Rittenberg days earlier.
Rittenberg's mother, Penny Kreitzer, heard about the tree through the news before she knew her daughter was involved. Kreitzer frantically called hospitals and was briefly hopeful when she couldn't find Rittenberg before learning the truth through a law enforcement official.
"I've lost a beautiful child through that tree," Kreitzer, told the Los Angeles Times. "I wish the tree had fallen on Saturday when no one was there."
There were about 300 campers and 150 staff at Camp Tawonga, which offers sessions for students in second through 12th grades. The camp is located on 160 lush acres on the Tuolumne River, just outside Yosemite National Park. It has been in operation since 1925, according to its website.
Kramarz said the children had been told only that a tree fell and some staff had been injured.
Moore is expected to be discharged on Friday, her father, Robert, said. She will be entering her sophomore year at Syracuse University after her summer break.
But Lizzie Moore said she wants to return to the camp in a week or two to say hello to everyone and let them know she's fine.
Follow Sudhin Thanawala at http://www.twitter.com/SudhinT. Associated Press writers Jason Dearen, Lisa Leff and Gosia Wozniacki also contributed to this report. Wozniacki reported from Fresno, Calif.