Newly released footage has shown how a dangerous killer "crab walked" up two walls separated by a 5ft (1.5m) hallway to escape a Pennsylvania prison.
Danelo Cavalcante, 34, has been on the run since 31 August when he fled from Chester County Prison.
His escape route involved climbing the same walls another inmate had scaled earlier this year to get away.
Officials say razor wire was installed after the previous escape, but that it was clearly not effective.
The Chester County Prison acting warden said at a news conference that the prison had hired security consultants after the 19 May escape of Igor Bolte, who told police that he had relied on his knowledge of rock climbing to escape.
The consultants had "identified an insufficiency", said Acting Warden Howard Holland, and razor wire was installed to keep other inmates from using the same exit route.
"While we believed our security methods were sufficient, they were proven otherwise. And we will now move quickly to enhance our security measures," said Mr Holland.
Cavalcante was sentenced to life in prison last month after being found guilty of brutally stabbing ex-girlfriend Deborah Brandao to death in April 2021 in front of her two small children.
His escape last week has made headlines in his native Brazil, where he is wanted over another killing in 2017.
Video shows how he "crab walked up a wall, through razor wire", Mr Holland said on Wednesday, placing his hands on one wall and his feet on another wall to push his way upwards.
After reaching the roof, both inmates were able to climb down a ladder to a less secure part of the prison.
Asked how it could be possible for an escape to be replicated so soon after the previous one, Mr Holland replied: "We thought we took appropriate efforts to prevent that with the razor wire."
But while the prison focused on the physical barriers, the acting warden said they had failed to address "the human element".
In May, an officer spotted Igor Bolte escaping on video monitors, and the inmate was caught five minutes later. At the time of Cavalcante's escape, just before 09:00 local time (1300 GMT), there was a corrections officer in the observation tower but he failed to spot him.
That officer has been placed on administrative leave and is under investigation by the state's attorney general.
Investigators leading the manhunt said on Wednesday that they have expanded their search perimeter amid several sightings in recent days.
Pennsylvania State Police Lt Col George Bivens told reporters that Cavalcante "may be having trouble navigating" through heavily wooded terrain and could be hiding in sheds or other out buildings.
On Monday, authorities began using helicopters and patrol cars to blast an audio message recorded by Cavalcante's mother in Brazil, in which she calls on him to surrender.
A $20,000 (£16,000) reward is being offered for information leading to his capture.