GRAND PRAIRIE, Texas -- Few police officers and convicted criminals can call themselves the best of friends. But that's the story in Grand Prairie where an ex-con-turned-success is thanking the officer who finally ended his run from the law.

The streets of Grand Prairie were once the playground of a young man named Keenan Williams, a high school dropout whose mugshots could fill their own book. He was a drug dealer, a crack addict, and an armed robber who was arrested and jailed 45 times.

So why, on a late October morning, was he the guest speaker at a meeting of Grand Prairie police supervisors?

"I went to prison for aggravated robbery," he told them. "I started kicking in drug houses and robbing people, that's why I got shot five times!"

"Because this is not supposed to happen," he said of the fact he was speaking to police that day. "This doesn't make sense."

It does make sense if you consider Keenan Williams' path to where he is today.

"I just started robbing drug houses because I knew all the drug dealers, because that's who I was," Williams told WFAA. "So that's how I ended up being shot so many times, being an idiot!"

But this isn't just a story about a self-professed reformed idiot. It's also a story about who the ex-con was sitting next to.

"I care about people. It's just who I am," retired Grand Prairie Police Department Detective Alan Patton said.

Back in 1993, with Keenan's world of drugs and guns and run-ins with the law closing in around him, Patton offered Williams his first moment of respect.

"Keenan reached out to me and asked for 24 hours to basically say goodbye to his family," Patton said. "I basically instructed the police officers in Grand Prairie to leave Keenan alone for 24 hours, and they did."

And so Keenan Williams, the drug dealer, the toughest thug in Grand Prairie, willingly turned himself in.

"When I talked with you on the phone that day, you were very respectful," Williams said as he sat side-by-side with Patton last month in a second floor room at the Grand Prairie Police Department. "You didn't judge me. You did your job!"

"You were not a bad police officer trying to arrest me because I was a black man. The way you conveyed it, for that moment, I accepted the responsibility of that crime. That sealed the deal for me," Williams said all these years later with tears running down his face. "I knew right then that my life was about to change."

"Because all this stuff is going through my head like 'Okay, I'm about to go to prison for a long time. But at least going to prison I'm not going to be doing crack cocaine anymore. I don't have to worry about hurting people anymore. I don't have to worry about people shooting me anymore,'" he said.

"I've always believed that [if] you give respect, you get respect in return," Patton said.

"You showed so much respect to me and when you did, I respected you," Williams replied.

Fast forward, through those six years Williams served in a Texas prison. He would read more than 200 books, get his high school diploma, pursue a college degree, and purposely practice the handshake he planned to give to the detective who put him away.

"But the first thing I said is, 'I'm here to thank you because what you did changed my life,'" he told the group of Grand Prairie police supervisors during his October presentation, recalling his first meeting with Detective Patton after he was released from prison.

Because that Keenan Williams is now a completely different Keenan Williams. He is a successful businessman, a finance specialist working with north Texas banks, a happy husband and father, a motivational speaker at prisons, at schools, and at police departments. He's even used that oft-practiced handshake as he made friends with some of the most important people in the country, including a visit with Texas Governor Greg Abbott.

"You protected them when you arrested me," Keenan told Patton of his memories of that 1993 arrest. "But you also protected me."

"And then to publicly say what he said about how we knew each other," Patton said of a public fundraising event where Keenan introduced Patton as the man who changed his life. "I knew in that moment I'd made a difference in a way that I couldn't imagine. My career was a success because I had something to do with this man making a change in the way he lived life."

"He's the poster-adult for what can happen if you're just shown a little mercy and grace from the person who's going to put you in jail and send you to prison," he said. "Keenan is a magnificent man and I'm very proud of who he is."

"That's the effect you have as a police officer," Keenan said in his Grand Prairie Police Department speech. "Because what he did in my life you can do in someone else's life," he told them.

So an ex-con tells his story of redemption to whoever will listen, even to the cops who helped put him away.

"I think it could give you the courage and the understanding that regardless of what a man is going through, you can never determine where he ends up," Williams said.

Because it might end up with a handshake and a thank you for a life saved.

But in this case Alan Patton would agree, maybe two lives saved.

"I'm proud of him like I would be for my own son," Patton said.