Mitchell Takata, 21, of Los Altos, faces charges of lewd acts upon a child under the age of 14, attempted sexual intercourse or sodomy with a child under the age of 10, and attempted rape of a victim with a mental/physical disability.
Police say officers responded to a home in the Ramona neighborhood of Riverside in late May for a report of a molestation that had just occurred.
The child was allegedly sexually abused by her behavioral therapist during the session. Takata remained at the home when officers arrived, Riverside police said.
Detectives assigned to the Sexual Assault - Child Abuse Unit (SACA) responded and assumed the investigation.
No further details were given about the incident.
Takata was arrested and booked into the Robert Presley Detention Center. He remains in custody with bail set at $1 million.
Charges have since been filed against Takata by the Riverside County District Attorney's Office.
Investigators say Takata has been employed as a behavioral therapist for about three years, working primarily with severely disabled children. Police believe there may be other victims who have not come forward yet.
Anyone with information regarding this investigation is urged to call SACA Det. Daniel Suarez at (951) 353-7120 or email DSuarez@RiversideCA.gov.