Agents with the state Inspector General's office have been trying to figure out how the convicted murderers were able to leave their cells at night to escape, and had been looking into whether guards had fallen asleep, officials have told CNN.
The admission that the inmates actually practiced making their way to freedom was the first of perhaps many shocking details officials hope Sweat gives up so they can understand how security broke down.
Clinton County District Attorney Andrew Wylie told CNN in an email that Sweat said that he and Matt started planning their escape in January. They cut through steam pipes to get to an underground tunnel system.
The night before they broke out, Sweat and Matt went through the tunnels and reached a manhole, but decided it wasn't isolated enough, Wylie said. They decided to escape from a different 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.
Three members of Clinton Correctional Facility's executive team, along with nine security staff employees, have been placed on paid administrative leave as part of the review of the escape, according to the New York State Department of Corrections and Community Supervision.
Superintendent Steven Racette and Deputy Superintendent Stephen Brown are among the executives on leave, a state official told CNN on Tuesday. The other is First Deputy Superintendent Donald Quinn, according to a source familiar with the investigation.
The official had been briefed on the convicts' elaborate escape from the maximum security lockup. For about three weeks, searchers combed terrain in upstate New York. On Friday, Richard Matt was shot and killed. David Sweat was shot and captured Sunday.
The FBI is investigating possible broader corruption at the prison
, law enforcement officials briefed on the case said Monday. Agents are looking into whether drug trafficking or other criminal behavior among employees and inmates took place, officials said. Some employees who have been questioned told investigators that there was heroin use among prisoners and an alleged drug trade involving employees.
A plan to head to Mexico?
Earlier, Gov. Andrew Cuomo said that the inmates had a plan: A prison worker, Joyce Mitchell, would pick them up after they broke out, kill her husband, and then the three would head to Mexico.
That's what Sweat told investigators from his hospital room in Albany, Cuomo said.
"They would kill (Joyce) Mitchell's husband, and then get in the car and drive to Mexico on the theory that Mitchell was in love with one or both of them," Cuomo told "The Capitol Pressroom" radio program
. "And then they would go live happily ever after."
Sweat's condition was upgraded to fair Tuesday, according to a statement on Albany Medical Center's Facebook page. Medical director Dennis P. McKenna says he will remain in the hospital for "at least a few days."
Sweat is in a locked-off section of the hospital, separated by secure doors, a spokesman said. It's a section designated only for prisoners. No other patients would be treated there as part of the hospital's contract with the Department of Corrections, according to Jeffrey Gordon, hospital vice president of communications. Sweat is not allowed to have visitors.
Photos taken shortly after his capture show him bloodied and in leg irons, wearing an oxygen mask and apparently conscious as he's tended to.
Prison workers charged
Mitchell is in jail, charged with aiding Matt and Sweat.
District Attorney Wylie has said that she smuggled hacksaw blades
and other tools embedded in meat through the prison's main gate and placed it in a freezer in the tailor shop where another prison employee, Gene Palmer, took the meat to an area where the inmates would be.
Palmer faces one count of promoting dangerous prison contraband,
two counts of destroying evidence and one count of official misconduct, a misdemeanor.
On Tuesday, Mitchell's attorney told CNN that she told him she was "ecstatic both that the manhunt has ended and also that it appears no harm came to any other person."
"She has been praying for this and she believes her prayers were answered," said Steve Johnston.
Shortly after the inmates broke free, Mitchell, who was supposed to be their getaway driver, hadn't shown up, Cuomo said.
She went to the hospital. Sweat, 35, and Matt, struggled to outpace searchers on their heels.
The two remained together for more than two weeks, Cuomo said. But eventually, Matt became a burden to the younger, more athletic fugitive.
"Sweat felt that Matt was slowing him down," Cuomo said. "Now we know that Matt had blisters on his feet because we found bloody socks. So that's possibly a reason Matt was slowing him down. And also Sweat was a younger man, and he was fit."
And evidence suggests Matt had been ill, possibly from contaminated food or water, a law enforcement source briefed on the investigation said.
By the time Matt was shot, Sweat had already left him behind. Police caught up with and killed Matt on Friday in Malone; Sweat made it within two miles of the Canadian border before he was captured Sunday.
"I still say to this day if that woman -- and whoever else was involved -- didn't give them that stuff, those guys wouldn't have ever broke out of jail," Sweat's mother, Pamela Sweat, told CNN's "Erin Burnett OutFront" on Tuesday. "My son could have been killed just like the other guy because they, more or less, let him loose. They knew what was going on, and they didn't stop it."
When asked what her hope and message for her son are, she said: "I just hope he learned his lesson, and he stays in where he's at, and I get to go see him."
"I hope that he gets better and I love him and I miss him," Pamela Sweat said.
Former FBI official: Mitchell would have been killed
But a former FBI assistant director cast doubt on the plan that Sweat described to investigators.
said he doubts Sweat and Matt really intended to kill Mitchell's husband and then drive with her to Mexico.
"I don't think they'd take the time to go divert to her house just to kill her husband, and I'm not sure why they would want to do that. That just wastes time," Swecker told CNN's "New Day."
And he said Mitchell's failure to pick up the escapees at the manhole likely saved her life.
"They would have had no use for her whatsoever," he said. "They used her, and they would have tossed her out right away. And then she would have been in a very shallow grave within hours."
Camouflage, maps and Pop-Tarts
Matt and Sweat were well-equipped when they were found.
Both were wearing camouflage. Matt was dressed in dark brown pants, a dark green jacket, and heavy boots when he was shot, Franklin County Coroner Brian Langdon told CNN.
"He was dressed for the woods," Langdon said. "He would blend right in if he stood still."
Matt's clothing was not torn or ragged, though Langdon did recall an odor of stale blood.
"I thought he was kind of well-kept for somebody who's been living in the woods for 20-some odd days," Langdon said.
Matt may have stolen clothing or other supplies from a cabin in Mountain View, where his DNA was found.
After Matt was killed, authorities could smell alcohol on his body from a few feet away, the law enforcement source said.
When Sweat was captured, he had a backpack full of supplies, Cuomo told CNN's "New Day."
"He had maps, he had a certain amount of tools, he had bug repellent, he had wipes, he had Pop-Tarts," he said.
It's not clear whether Sweat acquired those supplies before his escape, or whether he stole or collected them while on the run.
What's next for Sweat
Even though authorities want to know more about Sweat's plot and who helped him, it's unlikely he'll get a plea deal out of it, District Attorney Wylie said.
"There's certainly no plea bargain that we could put out there," he said. "The Department of Corrections obviously wants information ... whatever benefit that may be for David Sweat, only time will tell."
But Jeff Dumas, a retired sergeant at Clinton Correctional Facility, said he thinks Sweat might try to work out a deal by giving more details in exchange for getting less time in solitary confinement.
Regardless, it's unlikely Sweat will go back to Clinton, criminologist Casey Jordan said.
"He would never be safe there," she said.
A former inmate at Clinton agreed. Louis Ferrante said someone like Sweat would usually be considered a hero to many prisoners -- a convicted cop killer who pulled off a stunning escape.
But Sweat's "ratting" on misdeeds in the prison means other inmates would harass or hurt him, Ferrante said.
"That's going to do him a lot of harm," he said. "They're going to be spitting on him. He's garbage now."
Feds probe possible drug trafficking
The idea that a heroin ring was happening in Clinton Correctional didn't surprise former inmate Louis Ferrante
"I was in federal, state and county prisons. There wasn't a prison I was in that wasn't heroin-infested," he said.
"There is heroin use in every single prison. If the feds want to tackle this, they better get ready" to take on a nationwide problem.
Corrections officers have for years brought contraband into prisons for a variety of reasons -- sex, love, money, ego.
A former guard at Rikers Island told CNN recently that he wanted to make more money to pay off mounting bills and started selling cigarettes, then cocaine, in the jail.
Gary Heyward said he made a lot of money, but he also got caught and served two years in prison for what he did.
Prison guard goes to court
Matt and Sweat needed help in their escape -- namely, power tools to carve through a maze of barriers.
Mitchell has admitted to smuggling hacksaw blades by hiding them in frozen hamburger meat and having the meat delivered to Matt, a law enforcement official said last week. She has been arrested and charged with promoting prison contraband and criminal facilitation.
And Gene Palmer, a guard on the honor block where Matt and Sweat were housed, was arrested and charged with promoting prison contraband, tampering with physical evidence and official misconduct.
He appeared in court Monday and waived any more hearings in Plattsburgh Justice Court. The case will now go to a grand jury in Clinton County Court.
Palmer's former attorney has said the guard was unaware of the meat's contents when he was asked to get it to Matt.
The district attorney said Sweat made similar comments.
"From what I understand, in reviewing the reports (Monday), he told investigators that Palmer had no involvement in the escape," Wylie said. "It was just Mitchell, he and Matt."