Sam 'Machine Gun Preacher' Childers grew up in the hills of Pennsylvania. His parents were decent, honest people but at an early age Sam started to show a knack for getting into trouble. His father, a former marine, grew fond of saying, "Boy, somebody's gonna kill you one of these days!"

By his early teens Sam was constantly in fist fights, selling hard drugs and sleeping with married women. He continued to slide deeper into a life of violence and crime until he became a shotgunner - an armed guard for drug dealers. It was during this stage of his life that he met Lynn, a stripper who would later become his wife.

Sam, haunted by his father's words, became increasingly concerned that he was going to be killed because of drugs and slowly began to distance himself from his former life. He found a job in construction and prospered despite his continuing drug and alcohol habit. Lynn, meanwhile, returned to the Church she had forsaken as a young adult.

Sam also sought to re-establish his relationship with God and began to live a clean life. Slowly, things began to change for the better. Lynn gave birth to a healthy baby girl and Sam started his own construction business. Little did they know that their greatest challenge was just around the corner.

In 1998, Sam arrived in the South Sudanese village of Yei. The African nation was in the midst of the Second Sudanese Civil War, and Sam, urged by his pastor in the US, had joined a mission group to help repair huts damaged in the conflict. During this assignment Sam stumbled across the body of a child torn apart by a landmine. He fell to his knees and made a pledge to God to do whatever it took to help the people of South Sudan.

Sam returned to South Sudan several months later to run a mobile clinic. To fulfil his promise he ventured far across the nation, from the southern town of Yei to the eastern villages of Boma.

While passing the village of Nimule, on the Ugandan border, he said God had sent him a message: "I want you to build an orphanage for the children, God said. And I want you to build it here."

The local people though he was mad. At the time, the Lord's Resistance Army, a brutal rebel militia that had kidnapped 30,000 children and murdered hundreds of thousands of villagers, was laying waste to the area.

But Sam was adamant: God had told him to build the orphanage in Nimule and that was where he was going to build it.

He returned to the US, sold his construction business and sent the money to Africa.

Slowly the orphanage began to take shape. During the day Sam cleared the brush and built the huts that would house the children. During the evening, he slept under a mosquito net slung from a tree: the Bible in one hand, an AK-47 in the other.

Meanwhile, in Pennsylvania, Lynn and their daughter Paige fought a battle of their own. The family car was repossessed and a foreclosure notice was issued on the house.

Sam had enough money to pay the outstanding mortgage or finish the orphanage.

He couldn't afford both so he sent the money to Africa.

With the orphanage finished, Sam began to lead armed missions to rescue children from the LRA. It wasn't long before tales of his exploits spread and villagers began to call him the "Machine Gun Preacher".

Fifteen years later the orphanage is the largest in South Sudan and has fed and housed more than 1000 children.

Today, more than 200 children call the orphanage home.

Unfortunately there are still many Sudanese children suffering and in need of rescue.

Sam and Lynn still live in the same house in Pennsylvania and are just as dedicated to the plight of the South Sudanese children as they were 15 years ago.

Sam's biography, Another Man's War, was turned into the 2011 film Machine Gun Preacher, starring Gerard Butler.

He is currently on his Australian tour - details which can be found on his Facebook page Machine Gun Preacher.

The Christian School hall seats around 800 people and will be a first in, best dressed scenario.

There is no cost for entry, although any donations will be accepted on the evening.

The talk begins at 6.45pm.