Johnathan Miller, 27, was booked on suspicion of being an officer who engaged in "sexual activity" with a detainee, according to the department.
Deputies say that they started to look into Miller after "jail staff received information regarding inappropriate contact between a male deputy and a female inmate" at Glen Helen Rehabilitation Center.
Authorities served a search warrant at Miller's home and interviewed him.
Apparently they didn't like what they found or heard.
The deputy, who was put on paid administrative leave, posted $25,000 this morning.
Investigators want you to step forward if you have more info on this guy: 909-387-3589.