A Utah inmate jailed for allegedly raping a 13-year-old girl now faces charges for trying to hire a hitman to kill the teenager to keep her from testifying, police said.

Kristoffer Jones, an inmate at the Purgatory Correctional Facility in Hurricane, Utah, allegedly "solicited several inmates to either kill or assist in coordinating the murder" of the victim, the Washington County Sheriff's Office said in a statement.

He was booked Monday on two counts of criminal solicitation of murder following a monthslong investigation. Jones was being held on child sex offenses from an incident investigated in January.

Authorities said they were alerted to the alleged murder-for-hire plot through information gathered by deputies assigned to the prison's intelligence unit.

"With the aid of an undercover officer, sufficient evidence was gathered to support the fact that Jones had taken substantial steps from inside the correctional facility, to carry out the plot," the sheriff's office said.

Kristoffer Jones. Washington County Sheriff's Office

One inmate told detectives that Jones told him to "get rid" of the girl, the Salt Lake Tribune reports. The inmate, who was reportedly working with police, told authorities that Jones said "he knew people on the outside" who could help with the alleged plot.

Jones wrote a note to the man agreeing to pay him money within 30 days of his release if he went through with killing the teen.

According to the outlet, citing a probable cause statement, Jones "drew a map of the apartment complex and the specific building and apartment" where the teenager lives, as well as provided information on her parents' work schedules and what school she attends. He also said the teen could be killed by being hit by a car, in a drive-by shooting or by injecting her with insulin, according to the Salt Lake Tribune.

In a video call with an undercover officer pretending to be the hitman, Jones was offered a chance to back out of the plan but he insisted the girl be killed, the outlet reports.

During the investigation, police learned that Jones went to another inmate for help with killing the girl. Jones allegedly wrote a "written promise letter, sealed with a blood fingerprint" telling the inmate that he would help him rob a bank when they were both released.

The note went on to say: “I’m facing 25 to life for rape of a child that I never committed, & I need the b---- to disappear for good.”

The Washington County Sheriff's Office said in its statement that safeguards are in place to ensure the victim is safe.