A two-time murderer is suspected of killing another inmate, a Franklin County man, aboard a prison bus while it traveled south on Rt. 23 from Columbus on Wednesday evening.

The body of David L. Johnson, 61, was found in the Ohio Department of Rehabilitation and Correction bus when it stopped to deliver him to the Ross Correctional Institution, said Ross County Prosecutor Matthew Schmidt.

Johnson, who was serving an eight-year sentence for sexual battery, apparently was strangled; Casey Pigge, 28, is “absolutely the suspect” in the death, Schmidt said.

Other inmates also were locked into a caged section of the bus with Johnson and Pigge, but apparently did not alert the guards and driver at the front of the bus of the assault, Schmidt said. The guards apparently cannot see back into all sections of the bus, he said. The inmates were wearing handcuffs, and perhaps belly chains, but could move around, the prosecutor said.

Inmates, including from the Southern Ohio Correctional Facility near Lucasville and the Ross Correctional Institution near Chillicothe, were taken aboard the bus to Columbus for medical treatment on Wednesday and were on the return leg of the trip south when the apparent slaying occurred.

Pigge is serving a 30-year to life sentence at the Lucasville prison for the 2008 murder of Rhonda Sommers, 52, the mother of his then-girlfriend. Pigge was convicted of stabbing the woman and then setting her apartment on fire.

Last week, Pigge pleaded guilty to using a cement block last year to repeatedly strike and kill his cellmate, Luther Wade, 26, of Springfield, at the Lebanon Correctional Institution in Warren County. Wade was serving a 10-year sentence for aggravated burglary. Pigge faces another life sentence in the slaying.

Schmidt was critical of the Department of Rehabilitation and Correction, saying state officials have provided no information about Johnson’s death. He learned of the slaying in a Thursday afternoon email from the Warren County prosecutor. Schmidt said his knowledge of the case comes from State Highway Patrol investigators.

He questioned Pigge having access to other inmates aboard the bus given his history of violence. Investigators are working to determine if Johnson died in Franklin County, Pickaway County or Ross Country as the bus traveled south, Schmidt said.

“He crushed his cellmate’s head with a cinder block. You would think the sensible thing to do would be to make sure he doesn’t have free access to other inmates at any time. Apparently that is not an issue for the folks at DRC,” Schmidt said.

A prisons spokeswoman declined comment and referred questions to the State Highway Patrol, which provided a bare-bones incident report with no details.

rludlow@dispatch.com

@RandyLudlow