( CNN ) -- The man suspected of killing Colorado 's prisons chief was still supposed to be behind bars . But because of a clerical error , Evan Ebel was let out of prison in January -- four years early . Authorities suspect he went on to kill Tom Clements , who led the state 's prison system , last month . They have also said there is a `` strong connection '' between that killing and the murder of Nathan Leon , a pizza delivery driver who was found dead in suburban Golden , Colorado . `` The district has undertaken a review of its practices in an effort to avoid a reoccurrence of this circumstance , '' Charles Barton , chief judge of the 11th Judicial District , and Walter Blair , district administrator , said in a Monday statement . `` The court regrets this oversight and extends condolences to the families of Mr. Nathan Leon and Mr. Tom Clements . '' Ebel went to prison in 2005 . He was serving an eight-year sentence when he assaulted a prison guard . He entered into a written plea agreement , which stated Ebel would plead guilty to assault in the second degree and that the court would impose a consecutive sentence of up to four years plus a mandatory three years of parole . A sentencing hearing was held in June 2008 . Records : Ebel told prison guard 'she would beg for her life ' `` The judge announced a sentence of four years in the Department of Corrections but did not state it was consecutive because it was already required by the terms of the plea agreement , '' read Barton 's and Blair 's statement . `` Because the judge did not expressly state that the sentence was consecutive , the court judicial assistant did not include that term in the mittimus , the sentence order that went to the Department of Corrections . '' Noted Denver-area attorney Scott Robinson represented Ebel in four cases from 2003 to 2005 . They lost contact after that . `` If you were writing fiction , you might have trouble understanding this thing to be true . Catastrophic for three families -- the Clements , Leon and Ebel families , '' he said . `` What 's really agonizing about this situation is it was an utterly routine plea bargain . A mundane task a judge undertakes every single day . Here we are five years later looking at the wreckage that was the result of those errors . '' Clements was shot to death at his home outside Colorado Springs on March 19 . Ebel was killed two days later in northern Texas in a gun battle with authorities that left a sheriff 's deputy wounded . CNN 's Mark Morgenstein contributed to this report .
A court apologizes for the mistake , says a review of practices is under way . Evan Ebel is suspected of killing Colorado prisons chief Tom Clements . While serving an eight-year sentence , Ebel assaulted a prison guard .