Colo. Dept. Of Corrections / AP, file This undated photo released by the Colorado Department of Corrections shows paroled inmate Evan Spencer Ebel.

A clerical error made by the Colorado court system allowed the man believed to have killed the state's prisons chief to be released almost four years early.

Court officials acknowledged in a statement Monday the error that allowed Evan Spencer Ebel to be released January 28.

In 2008, Ebel pleaded guilty to assaulting a prison guard while serving time for breaking into a car, having an illegal gun and carjacking a man. His four-year sentence was supposed to have been served consecutively after the the eight-year sentence he had been serving.

But a court clerk entered the sentence as concurrent to the one he was serving, which led Ebel's January release.

He is suspected of killing Tom Clements, executive director of the state Department of Corrections, on March 19. Clements was shot dead apparently after answering the doorbell at his home outside Colorado Springs.

Ebel is also suspected in the March 17 killing of a Domino’s pizza delivery man outside Denver. Authorities have speculated that Ebel used the man's uniform to get Clements to come to the door.

A Domino's uniform was found in the car Ebel was driving when he was killed in a shootout with deputies in Texas on March 21.