Every day in his cell in one of the most notorious prisons in Latin America, an American father wrote a letter to his little boy. Jason Puracal would tuck the papers away, trying to fight the fear that his son might grow up never knowing his dad.

"Jabu was my sunshine. My ray of hope. When I was in there -- it was dark ... it was so ... hard ... I just imagined I could see him," Puracal told CNN on Monday night via phone from New York.

Puracal seemed to choke up a little. After all, he was speaking less than two days after gaining the freedom he thought he'd never have again -- the result of a Nicaraguan court system ruling last week that his conviction could not stand.

Puracal took a breath and laughed. He lovingly shushed the loud giggles of his 5-year-old.

"Come on, play!" the boy said as he tugged at his father.

Puracal, from Washington state, had been behind bars since November 2010, when Nicaraguan authorities raided his real estate office in the coastal tourist city of San Juan del Sur and accused him of money laundering, drug trafficking and involvement in organized crime. He was sentenced to 22 years in August 2011.

Puracal survived "day by day, minute by minute," he told CNN's Anderson Cooper in an exclusive interview Monday night.

"It's a fight for your life every second of the day," he said.

For nearly two years, a chorus of supporters -- including a former FBI agent, a U.S. congressman and several noted human rights attorneys -- fought to clear Puracal's name. They said that there was no evidence to support the charges and that the American's prosecution was rife with legal mistakes and misconduct.

Read the details of Puracal's case

Earlier this summer, Puracal's defense team presented their arguments before an appeals court in Nicaragua, which decided last week to vacate all charges against him.

One of Puracal's attorneys picked him up from the notorious La Modelo prison near Managua late last week and drove him out of the gates. Puracal immediately took a hot shower, and then another and another.

The prison is notorious for its harsh treatment of inmates and for housing some of the region's most violent criminals. Puracal said he had been beaten and been refused water and food for days at a time and had developed a painful inflammation in his bowels and lost a lot of weight.

Puracal talked about the experience with Cooper on Monday night.

"It is a notorious prison -- just the conditions and overcrowding of it and the danger of it. What is that first moment like when the gate slams behind you and you realize the reality of where you are?" Cooper asked.

"I was with rapists, murderers and actual drug dealers," Puracal said. "It's a very violent place. There's a lot of tension between different groups in there; not only the conditions, but the other people around you."

There were times, in the beginning, when Puracal just couldn't believe what was happening to him.

"I didn't believe that I was there, and I kept thinking to myself, 'Oh this is just a big mistake' and that they will let me go any day now," he said. "And the whole time, 'Oh yeah, any day now I should be going,' and it just kept dragging on and dragging on."

What is it like being a free man?

"It's wonderful ... it's very overwhelming," Puracal said. "But I'm happy to be back with my family my wife and my son. ... It's still very, very surreal. The whole experience has been very unbelievable."