The suspect was expected to make a first court appearance on Monday in juvenile court in the death of 11-year-old Terry Dewayne Smith Jr., whose disappearance Sunday led hundreds of volunteers to search for four days in triple-digit heat.
On Wednesday, authorities announced they had found a body matching the description of Terry Jr. in a shallow grave under a tree behind the house he shared with his mother, half-brother and other family members.
Riverside County prosecutors have also asked for a court hearing to determine whether the half-brother should be tried as an adult, said John Hall, a spokesman for the district attorney's office.
The Associated Press is not naming the suspect because he is a juvenile.
Initial reports from the mother, relayed by law enforcement, described Terry Jr. as an autistic boy who took special medication and answered only to his nickname, "JuJu."
His father, however, insisted that his son was not autistic.
The boy lived with him until 2011, when he went to live with his mother, and was a normal kid who loved video games and baseball, said Terry Dewayne Smith Sr., a 62-year-old retired truck driver living in Charleston, W. Va.
"He was a very bright, well-adjusted child, at least he was when he left here," said Smith Sr. "He pushed buttons and would aggravate you. But, other than that, it was just the typical way ... of a typical boy trying to get his way."
Smith Sr. also helped raise the half-brother accused in the case, he said. The teen moved from West Virginia to California after his mother abruptly pulled him out of school, he said.
"I taught him how to walk. I helped him when he was on the baseball team here," he said, recalling that he called the half-brother "little Spider-Man."
A phone listing for the boy's mother, Shawna Smith, was disconnected. Messages left at a second number associated with her address were not returned.
Investigators told Smith Sr. that Terry Jr. died after a hit to the head but declined to say more, citing a request from police who are still working the case.
Hundreds of volunteers searched for Terry Jr. for more than three days in abandoned trailers and campsites tucked into the scrubby hillsides of rural Riverside County, where horse ranches dot the landscape and large stretches of land remain undeveloped. Sheriff's deputies fanned out on horseback and with bloodhounds in the triple-digit heat and helicopters buzzed overhead, searching for clues.
A detective involved in the search gave credit for the discovery of the body to a volunteer woman who said she had a vision of where to find Terry.
Detective John Powers told KFI-AM radio on Thursday that Pam Ragland and her children came to the property where investigators, including him, had searched thoroughly already and found the body immediately.
"She actually went right up the driveway of the house, on to the property, and right up to the body of this boy," Powers said. "Not in 23 years have I ever seen anything like this."