Jody Thompson first came into contact with his now son when he was off duty in 2015. He was pulling into the car park at the Poteau Police Department in Oklahoma to drop off his partner when he overheard a dispatch about a case of physical child abuse.

Despite not being on duty, Mr Thompson offered to respond to the call, given his experience handling child abuse cases during his time working at the district attorney’s office.

"I've investigated child abuse cases before. I thought I'd better go ahead and respond,” Mr Thompson told CBS News.

He arrived at the scene to find a severely underweight boy, called John, whose wrists had been bound by belts and who was covered in bruises.

The eight-year-old, who weighed just over four stone at the time, had been immersed in a dustbin full of cold water.

"He did not have a spot on his body that didn't have a bruise or abrasion. It was the worst thing I've ever seen,” Mr Thompson said.

The officers then took John, covered in a blanket, to an Oklahoma Children’s Advocacy Centre so detectives and investigators could take photos. He then drove him to hospital, where he sat by his side all night as the child recovered in the intensive care unit.

"I sat with him. And when he was admitted to the intensive care unit, I sat all night until the next day," he said.

The following day Mr Thompson contacted the Oklahoma Department of Human Services (DHS) to request he become the child's foster parent. Within just a few days, he had brought John into the safety of his own home.

"When I'd seen him in that house shivering and his hands tied - just soaking wet and confused - I knew at that moment the only time I would be satisfied and sure that he was safe is if he was with me," he said.

The officer, who already had 15-year-old and 8-year-old sons, said he did not tell his family initially but that they had faith he was doing the right thing before they heard the harrowing story.

In another extraordinary twist, just two days after bringing him into the family home, he found out his wife was pregnant with their third biological son.

In another unlikely turn seven months later, DHS called the Thompson family to ask them if they wanted to foster John’s newborn sister, Paizly, who had been born in prison with his mother.

They picked her up from the hospital the next day - when she was just a day old - and brought her straight home.

Although John's biological parents, who are both in prison and awaiting criminal trials, had relinquished their parental rights to their son, they refused to do so for their daughter, which led to a jury trial, where John testified on his own behalf.

It was not until February of this year that the Thompson's were formally allowed to adopt Paizley.

Last week, Mr Thompson received a certificate of commendation from the Oklahoma Bureau of Investigations, with John standing by his side as he accepted it.

Poteau Police Chief Stephen Fruenr released a statement, saying: "Jody's actions as well has his families are second to none. The example of love and compassion he has shown to this young man and his sister is an example everyone should follow.

"It's men like you that make me proud of our law enforcement brothers and sisters. You are very deserving of this commendation. I am proud to serve with you."

The inseparable father and son duo only recently opted to share their story with the world in the hope of helping other victims of abuse.