SAN MARCOS -- A developmentally disabled man who had been missing since Thursday was found on a steep slope near the Lake San Marcos dam Friday afternoon, authorities said.

A sheriff's helicopter crew spotted Derrick Post, 20, on a rocky outcropping around 4:30 p.m., said Sheriff's Department Search and Rescue Coordinator Sgt. Don Parker. The helicopter landed nearby, and after a crew member confirmed Post was in fair shape, search and rescue volunteers hiked down, Parker said. One volunteer carried the 4-foot-8-inch Post up the hill on his back.

Post, who authorities said has the mentality of a 7- to 10-year-old, did not speak to anyone and it was unclear if he had fallen off a ridge or climbed to the spot where he was found, Parker said. He went to Palomar Medical Center for evaluation and treatment.

Before he was found, Post had last been seen about 2 p.m. Thursday at Lighthouse Road and Glencrest Drive, about a mile from where he was found, Parker said. At that time, Post had been dropped off at home but ran away from his mother in some kind of game, Parker said. Post's mother said the young man was playful and friendly, but frightens easily and tends to hide when scared.

On Friday, as the helicopter crew helped Post, a man, possibly a hiker, called out and made his way to the area, Parker said.

He had broken his ankle and needed help. Fire department personnel rigged a rescue basket and volunteers helped pull the man to safety.