Evan Ebel's bracelet, worn as a condition of his release to confirm he was obeying curfew, signalled on 14 March that it had been tampered with.
But officials did not determine he had absconded until five days later - hours before Tom Clements was shot dead.
Ebel, 28, was killed in a shootout with Texas police three days after that.
Also, on Monday Colorado officials acknowledged Ebel was released from prison four years too early due to an apparent courthouse clerical error.
The confusion stemmed from whether he had been ordered to serve a consecutive or simultaneous prison sentence for assaulting a prison officer while incarcerated for an earlier crime.
Clements's death was the second in a series of three killings of US justice officials, including a Texas prosecutor and his deputy, just weeks apart.
According to court documents released on Tuesday in Colorado, Ebel had followed the conditions of his parole without incident since his release in January, checking in by phone every day and even once calling parole officials because no-one had requested a weekly drug test.
He worked for his father, a well-connected lawyer, and lived in housing his father had found.
"From 28 January to the middle of March, we had an individual who was calling in every day, who was employed, who showed no indication that he would do the kind of things that we now know," said Tim Hand, a spokesman for Colorado's parole division.
But on the afternoon of 14 March, the electronic radio monitoring bracelet he had been ordered to wear registered a "tamper alert". Later, he failed to report to officials as required to have the device repaired.
Parole officials did not speak with Ebel's father until 18 March. He told them he feared his son had absconded and gave them permission to search the younger Ebel's apartment.
The next day, officers found Ebel had fled - and taken a large amount of clothing. They listed him as absconded and obtained a warrant for his arrest.
That evening Clements, 58, was gunned down after he was called to the front door of his home near the city of Colorado Springs.
Authorities now say Ebel used the same gun to kill Clements that he used in the 21 March shootout in Texas in which he was shot dead by police.
Ebel is also suspected in the 17 March killing of Nathan Leon, a pizza delivery man and father of three.
Ebel first went to prison in 2005 for robbery, assault and car jacking. He was sentenced to three separate prison terms, all to be served at the same time, and scheduled for release this year.
While in prison he is said to have joined a violent white supremacist prison gang, and official documents state his body was covered with Nazi-themed tattoos.
Also while incarcerated, in 2008 he pleaded guilty to assaulting a prison officer and threatening his family. For this he was sentenced to up to four additional years.
According to court transcripts, Ebel told the judge that would make him 33 when he was released. The judge told him that four extra years was fair.
But in a subsequent court filing, the term was not specified as consecutive, meaning his sentence was automatically recorded as simultaneous. Prison officials say they had no way of knowing the judge had intended to keep Ebel behind bars beyond 28 January.
In a statement, the chief judge and administrator of the judicial district said they regretted the oversight and extended "condolences to the families of Mr Nathan Leon and Mr Tom Clements".
Those condolences were not well-received by Leon's widow, Katherine Leon.
"How do I tell my four-year-olds, 'Daddy was murdered because of a clerical error'?" she told local broadcaster KUSA.
An ex-convict suspected in the death of Colorado's prisons chief shed a parolee monitoring device days before the murder, officials have said.