One of the two convicted murderers who escaped from an upstate New York prison in June has revealed exactly how he and his partner managed to execute their elaborate prison break and then hide out from authorities for three weeks.

The convicted killers, David Sweat, 34, and Richard Matt, 48, escaped from the Clinton Correctional Facility on June 6, using power tools that were allegedly given to them by Joyce Mitchell, who worked at the prison. The men then went into hiding for three weeks before Sweat was captured and Matt was fatally shot by law enforcement officials in Franklin County, New York last Friday.

After being captured and hospitalized on Sunday, Sweat has allegedly told investigators how he and Matt pulled off their grandiose prison escape and eluded authorities while on the run.

Sweat, who is currently recovering from a gunshot wound at Albany Medical Center, said they began plotting their escape in January, Clinton County District Attorney Andrew Wylie told CNN.

After the two prisoners spent five months strategizing, they made a practice run and escaped through a manhole.

"To make a dry run and ... have the ability to escape, and then go back in, it is a little baffling," Wylie told NBC News.

Although it's not entirely clear how prison guards did not notice what was going on, the state Inspector General's office are looking into whether the guards had fallen asleep, officials told CNN.

Sweat also told investigators he and Matt were only equipped with hacksaws to carve through their cell walls and a steam pipe inside the prison, the district attorney said.

Sweat said that their original plan was to flee to Mexico before they split up last week, according to New York Gov. Andrew Cuomo, during a radio interview on Monday.

"The plan was to head to Mexico, which would have been aided by Joyce Mitchell's vehicle," Cuomo told WCNY in Syracuse. "They would get the car and then drive to Mexico."

"When Mitchell doesn't show up, the Mexico plan gets foiled and they head north to Canada," Cuomo added

The governor added that Sweat split up from his partner because he felt like "Matt was slowing him down."

Following their successful prison break, Sweat also told authorities he and Matt listened to radio reports about the manhunt, a state police source told ABC News.