Fatal mistakes exposed in Colorado killings?

Programming note: On Thursday Anderson Cooper talks with the wife of slain Colorado prisons chief Tom Clements. Tune in for the exclusive interview at 8 and 11 p.m. ET.

CNN's Martin Savidge reports on Evan Ebel, the murder suspect who shouldn't have been paroled, and should never have slipped out of reach.

Due to a clerical error, Ebel was released from prison four years before he should have been freed. He was serving time for armed robbery, and records show he was no model inmate. He threatened to harm or kill prison authorities several times.

Police believe he's behind the murder of the Colorado prisons chief. Tom Clements was gunned down at his home last month. Ebel is also suspected of killing Nathan Leon, a pizza delivery driver.

Documents obtained by CNN show it took Colorado officers five days to realize a paroled Ebel had disabled his ankle monitor and fled. The day they began the process of revoking his parole was March 19, the day Clements was murdered.