After questioning Barnhill about his involvement in the 2002 murder of Troy Neidhart, agents arrested Barnhill for first degree murder.
Agents said Barnhill is headed to the McClain County Jail where he will be booked in on a complaint of murder in the first degree.
Authorities said other arrests in this case are possible. Barnhill and Neidhart were acquaintances, according to investigators. Neidhart's skeletal remains were found in a rural area of McClain County nearly two years after Neidhart was reported missing to the Oklahoma City Police Department.
Investigators recently launched another effort to search for remains in McClain County this month.
The Office of the Chief Medical Examiner identified the remains as Neidhart's in 2006.