Scott Greene has changed his not-guilty plea and has pleaded guilty this (Friday) morning to ambushing and killing two Des Moines area police officers.

Greene will now avoid a September trial, after pleading guilty to two charges of first-degree murder in the deaths of Des Moines Police Sergeant Anthony Beminio and Urbandale Police Officer Justin Martin, last November.

Greene was sentenced to two consecutive terms of life in prison.

MORE: At a news conference after the hearing, Polk County Attorney John Sarcone revealed new details of the graffitti the double-cop killer scrawled on his cell walls.

"He drew pictures of each officer's face.  Making 'em sad and put their names on 'em.  He wrote 'Greene 2, Urbandale P.D., Des Moines P.D. zero'.  He had a picture that would be like your heartrate and then it going flat saying 'Thin blue line'," says Sarcone.  "Over the door of his cell, he put 'Red rum', obviously 'murder' backwards.  He had the initials of the officers over his bed with an R.I.P under it.  And, he had a hit list of people he wanted to take care of." 

Sarcone says his own name was on that hit list, along with the fallen officers' names checked off and three other prison staff.

Scott Michael Green unexpectedly pled guilty to two counts of first-degree murder during a hearing this morning in the ambush killings of Sergeant Anthony Biminio and Officer Justin Martin He was sentenced to two consecutive life sentences.

You can see pictures of Greene's graffitti below.

Polk County Prosecutor outlines murders