The sheriff's office responded to a report of a possible drowning at the beach, located near 9000 River Road, at 2:45 p.m., Lt. Steve Brown said.
A 15-year-old girl said her 13-year-old brother was in distress in the river before he went under water, Brown said.
He was pulled ashore by someone swimming in the river, and a citizen tried to revive the boy before paramedics arrived, Brown said. It was initially reported that the boy was under water for more than five minutes.
The boy was taken by ambulance to Sutter Medical Center of Santa Rosa then by helicopter to Children's Hospital and Research Center in Oakland.