An inmate already held at a maximum security prison in Minnesota was recently sentenced to 40 more years behind bars for strangling another inmate to death with a shoelace.

Benjamin H. Beck, 40, was convicted after pleading guilty to second-degree murder Thursday at a court in Washington County, where the Oak Park Heights maximum security facility is located. Beck was already serving time for burglary and assault charges from 2007, according to

Beck reportedly strangled 30-year-old inmate Shane Cooper because he found out that Cooper was convicted for raping a child.

Beck was reportedly Cooper’s “protector” in prison.

"When he found out why (Cooper) was incarcerated, (Beck) indicated to the agents that he could no longer be a protector of someone who had committed this type of crime and that (Cooper) did not give him a way out," read a criminal complaint.

Prison officials found Cooper dead in his cell and checked surveillance footage to find that Beck killed him.

Beck said that no other inmates knew about the crime.