A man who allegedly r*ped his girlfriend’s four-year-old boy to death faces the death penalty, Daily Star UK reports.

Keith Jordan Lambing, 20, was arrested and accused with the monstrous crime over the death of his partner’s son Bentley Miller.

Bentley was found unconscious in the car of Kristen Herold, Lambing’s mother, with brutal injuries.

The tot was taken to hospital but died of injuries sustained as a result of the alleged attack including, internal bleeding.

Lambing’s mother has also been charged over attempting to cover-up his crimes.

Prosecutors confirmed the boy had been raped and beaten in Butler County, Pennsylvania, US.

Police tracked down Lambing and arrested him on Wednesday evening at an abandoned house.

He has been charged with homicide, r*pe and multiple assaults.

District Attorney Richard Goldinger said he is seeking the death penalty for Lambing if he is found guilty.

He said: "It’s unimaginable someone could do something like this to any human being, let alone a 4-year-old.”

Lambing’s mother was charged with endangering a child’s life and assisting an offender.

Lambing has a four-month-old child with Bentley's mother Mackenzie Peters.

She may also face charges, according DA Goldinger.

The infant has been taken into protective custody.