Chris Vogt wept as he discussed his past.

Vogt is prisoner 100765, and he is doing hard time. In 1998, he was sentenced to 48 years in Colorado prison for second-degree murder. "I am in prison on a murder sentence that I'm guilty of," Vogt emotionally told ABC News.

But for the families of nine autistic children, this convicted murderer is something of a savior. He has helped turn their lives around.

Since 2002, Colorado Correctional Industries has provided its inmates abandoned dogs to train, through a program called Colorado Cell Dogs, profiled in the documentary " Saving Castaways."

Prisoners have learned to train service dogs for the blind and deaf, but Vogt took it further. With nothing but time on his hands, he read all he could about autism, and came up with unique training techniques for service dogs-aimed at helping autistic children overcome behavioral and emotional issues.

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The dogs come from local shelters and Vogt trains them inside his cell, acting out problem behaviors himself. He trains each dog to meet a specific child's need.

He taught one dog to help nuzzle a child, so she would sleep at night. And he trained another to nudge and snap a child out of his fits and tantrums.

Arthur and Susy Tucker, the parents of Zachary, 9, were desperate for anything that would help their son with his Asperger's syndrome. He was refusing to be touched and his emotional anxiety sometimes ran so high that he would curl up into a ball on the floor during class.

"I'm no autism expert, but I'm a teacher who works with kid with disabilities every day, and Zachary was bad," said Erin Carroll, Tucker's teacher. "He would crunch down in a fetal position at his desk, he wouldn't talk, he was inconsolable."

On weekends the family started sending their son 200 miles to the high-security prison to work with Vogt, and eventually to take home one of his dogs.

Tucker's new dog, Clyde, is trained to nudge and poke whenever he feels anxiety building and the process seems to be working.

"My anxiety has been brought down by at least 70 percent and I've been calm enough to socialize with kids, which I haven't been able to do in a long time," Zachary said.

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Now Zachary and his dog Clyde are suddenly the cool kids at school. Before, he was a troubled student failing in class. Today he's reading at grade level, and his math and science skills are off the charts.

"He's really advanced in science, in math," said one of Zachary's classmates. "He knows more than I do!"

The boy and his family traveled back again to the prison with ABC News, to meet the convicted murderer who made such a difference. The boy, who never liked being touched, gave the prisoner a hug.

"Here's a man that isn't allowed any physical contact," said Susy Tucker. "And yet [Mr. Vogt has] given my son the ability to hug and to care about other people and he can now do this for you."

"He made a mission out of helping our son," said Arthur Tucker.

From his prison yard, Vogt spoke of redemption.

"This is thing I do to give back," Vogt said. "When Zach and even the other kids get to work with me, they don't get to see the murderer. This has given me a chance to do something better."

ABC News