Nicholas Farber was found Friday at a campground in Jamul, about 20 miles east of San Diego. His mother and an unidentified man were arrested, authorities said.
"We have great news. We have Nicholas and he is safe," Riverside County Sheriff-elect Bob Doyle said.
The boy was abducted at 2 a.m. Wednesday by two men who broke into the home of Nicholas' father, Michael Farber, beat him and took his son, who was wearing only his underwear. The operation was described by police as
swift, violent and well-planned. A day later, authorities named the boy's mother, Debra Rose, and her former roommate as suspects.
Authorities had been searching for a motor home with Florida license plates believed to be carrying the boy. The motor home was described in an Amber Alert, the statewide notification system for child abductions.
Harold Stayton, a security guard at the Thousand Trails park, told The Associated Press he remembered the description of the motor home from news reports when he saw it in the park in a remote location amid dry, scrub-covered and boulder-strewn mountains 80 miles southwest of Palm Desert.
Stayton said the license plate was initially obscured by a flap over the motor home's fuel tank. Lifting the flap, he spotted a Florida license plate and called police.
Authorities began massing at the park, then quietly evacuated neighboring campers before knocking on the motor home's door.
FBI Special Agent Richard Garcia said Rose and the man initially refused to come out, but surrendered peacefully after they saw deputies had surrounded the vehicle.
Rose, 38, and the man, possibly one of the kidnappers, were arrested. The man was not immediately identified.
Mother and son were returned to Palm Desert together, and television footage showed her kissing the back of her son's head after they were placed in a patrol car.
Later they were transferred to a helicopter for the trip to Palm Desert, where Nicholas was reunited with his father and Rose was jailed.
As Rose was hustled into jail, a reporter asked why she had taken Nicholas and she replied: "He was taken from me."
Rose had altered her appearance, cutting her blonde hair and dyeing it a darker shade, and authorities said Nicholas' hair also appeared to have been cut and dyed.
Doyle said investigators were continuing to search for others involved in the kidnapping, including Rose's former roommate, Carla Bender of Colorado Springs, Colo.
The motor home was registered to an Orange County woman identified only as the neighbor of Rose's aunt, Julie Dohle of Laguna Niguel. She was being questioned by FBI agents, a source close to the investigation told The Associated Press. Dohle had been questioned earlier, the source said.
Sheriff's deputies towed two vehicles - one belonging to the neighbor, another belonging to Dohle - from the upscale Orange County neighborhood.
"We have been extremely worried and upset regarding the actions of the past couple of days. We are very happy Debbie and Nicholas have been found and are safe," said Dohle in a written statement.
Park security manager Shirley Charpentier said the motor home arrived at the campground late Wednesday night. The occupants had registered under the name Benvenuto and planned to stay until at least Saturday, according to a campground registration form posted in the window of the motor home.
Nicholas was the subject of a custody dispute between Rose and Farber, 47, who married in 1991 and divorced in 1996.
The boy lived with Rose until she was arrested on Aug. 15 in Colorado and held briefly for allegedly violating a restraining order involving another ex-husband. Farber went to Colorado and got Nicholas, then was granted temporary custody by a California court, which scheduled a Sept. 5 hearing on the father's bid for permanent custody.
The boy's mother was declared a suspect Thursday after her pickup was found at a Primm, Nev., casino. A $46,000 reward had been posted for information leading to Nicholas' whereabouts.