"Luke" is the perfect investigator. His likeable, unassuming manner is disarming. You'd never suspect he's spying on you.

Luke is not his real name. We can't identify him for safety reasons.

"I am part of the Animals Australia investigation team," he told 7.30.

"My work is to gather evidence that can assist in bringing about positive change in the treatment of animals."

Equipped with little more than his phone, a scooter and a small video camera, Luke has spent four months infiltrating and documenting on video, for the first time, the unfathomably brutal dog meat trade in Bali.

This is how he did it.

Warning: the rest of this story contains images and descriptions that some people may find distressing.

Gaining the dog hunters' trust

These dogs were bound and kept in a pen before being killed. ( ABC News )

"I began the investigation by pinpointing and getting to know the key players in Bali's completely unregulated dog meat industry. Eventually they invited me to join them as their gangs stole, hunted, poisoned and killed dogs.

"They believed I was interested in filming the preparation of local cuisine. That enabled me to have access to all aspects of the trade, from catching, to slaughter, to the butchering of dogs.

Pretending that I wasn't devastated every time that I saw a dog being horrifically abused was one of the hardest things I have ever had to do as an investigator.

"I have trained myself to cope with cruelty, but nothing prepared me for the brutal catching of dogs in a village. I focussed on my camera work but it was absolutely gut-wrenching to hear these dogs voice their sense of betrayal. They were literally screaming and wailing in terror and sorrow.

"The urge to intervene as defenceless dogs were being shot, bludgeoned or hung was almost overwhelming. But jumping in and helping that one animal might make me feel better, but it won't stop another and another from enduring the same fate and this shocking cruelty continuing for years to come.

The dog meat industry is growing

Luke has investigated the dog meat trade in Bali for four months. ( ABC News )

"While initially the eating of dog meat was restricted to ethnic minorities, unfortunately it is becoming popular amongst the Hindu population. It doesn't help that it is cheap and the western influence in Bali has made locals think that eating meat equals status. And, of course, you market any product as increasing men's virility, no matter how unfounded, and all of a sudden it becomes popular.

"Aside from the cruelty, the greatest shock was to discover that tourists are unwittingly eating dog meat and fuelling the trade. The average tourist coming to Bali has no idea that 'RW' on the outside of popular street food stalls indicates dog meat.

Mobile dog meat vendors are trawling popular beaches in Bali selling satays from buckets, deliberately not telling people the origin of the meat and when asked, they lie.

"A group of Aussie tourists enjoyed the dog meat satays so much they went back for seconds. Yet had they known the origin of the meat they would have been sickened.

'I found myself apologising for the cruelty of my fellow man'

A dog eats a cyanide-laced fish head. ( ABC News )

"I'd been spending time with a gang that was known for supplying large numbers of dogs to many restaurants throughout Bali. They had a reputation for being tough and 'efficient'. For quite some time, they wouldn't let me watch them in action, nor would they discuss their methods around me. But eventually, as familiarity grew, they opened up.

"I remember they complained that, while they would usually use poisoned baits to collect large numbers of dogs, they'd recently struggled to get access to the poison they needed. Finally, the day came when they invited me to join them on a collection. It was a reasonably disorganised operation and only a few gang members came along as most of them were reluctant to let me film them.

"I think they realised while the killing of dogs with poison was an effective way to hunt dogs and make money, that the poison would then remain in the meat that was being consumed. This is why documenting this was a critical part of our investigation. Even if the Bali Government didn't care about the cruelty, surely they would care about poisoned meat entering the food chain.

What I saw that day will remain burned in my mind for years to come.

"Poisoned baits were laid on a dirt path amid the labyrinth of Denpasar's back streets. Before long a lean and timid black dog appeared and ate one. The bait acted to 'stun' the dog and a gang member quickly grabbed him by the front leg while another leapt in to shove more poison down his throat. He began foaming at the mouth and collapsed as he tried to escape.

"While the effects of the poison were rapid, the dog's death was slow and it was obvious he was wracked with pain. Eventually, his laboured breathing stopped and he was dead. The gang quickly took to him with a blow torch to burn off his fur.

"Even as the dog's legs were cut off his body, a gang member announced that another dog had taken a bait. As I repositioned myself to capture this on film, I was gutted to see it was a small white puppy who was eating the poisoned treat. It took many agonising minutes for the puppy to die, and for the first time in my career, I turned off the camera. I sat stroking him as he died and found myself apologising for the cruelty of my fellow man.

"I feel for the people in all this too. I find that blank look that I so often see in the eyes of those inflicting cruelty on animals incredibly sad. Very few people in this world want to be cruel. Most of the time those who cause animals harm have just found themselves trapped in a 'system' and can't find their way out.

The dog catchers

Sorry, this video has expired Dog catching in Kintamani. WARNING: This video contains footage that may be distressing for some people.

"During the investigation, I visited a small dog meat restaurant in Bali's north. There I met the owner's son, a vibrant, rotund man of around 35 years old whose name was Made. I asked Made where his father got the dogs from. He admitted to being a dog hunter and said he supplied all the restaurants in the north of Bali.

"Made told me he caught most of the dogs he killed in Kintamani, an area famous for its beautiful scenery and active volcano. He invited me to join him in two days' time.

"The men prepared their tools. White rice sacks, pre-cut strings and wire nooses on heavy steel poles that appeared very well used.

"The first target was a dog a fellow intended to sell 'before [his] sister woke up'. He said his young sister's dog cried at night and kept him awake. The hunters crept up to the house, but the dog detected them. He barked and ran away. I rounded the corner to see a sleepy young girl holding the dog by the ears. She reluctantly allowed the dog hunters to noose her pet, drag him away from her and tie his legs together and his mouth shut.

The young girl looked on as the dog wailed in fear while the hunters stuffed him inside a white rice sack. They paid her brother 40,000 rupiah ($4) and left.

"The catching was fiercely aggressive. At times, one dog hung from the wire noose while another was tied. The hanging dogs screamed and writhed as the noose was strangling them. Some tried to bite through the ties to free themselves but with their muzzles lashed, their attempts were futile. The villagers accepted 100,000 rupiah ($10) for all nine animals. The terrified dogs were bagged and loaded onto the motorbike and the hunters headed off on their bikes back to their restaurant.

The man who shot dogs in open streets

Sorry, this video has expired A dog catcher shoots a dog in Bali

"On a cool, still morning in Bali, I met with Gus — short for Gusti. He was a member of a gang that I had recently met and he had invited me along to watch him collect dogs. I assumed Gus would noose dogs the same way I'd seen other hunters do, so it was a surprise when he greeted me with two puppies and a large rifle. He patted his puppies goodbye in a way similar to my own mourning ritual.

"We drove through the streets of Bali looking for dogs that suited his requirements. We passed many in the streets and I struggled to understand how they differed from the ones he would eventually take.

"Soon a suitable dog caught his eye. We stopped our motorbikes, he loaded his rifle and we turned back towards his target.

I asked Gus how he knew this dog was a stray. He responded, 'I don't care, I will just take it'.

"Luckily for that dog, two young men appeared at just the right time. Gus lowered his weapon and quickly sped away. Along the way, Gus kept getting calls from fellow gang members in different streets. We joined two of them in front of a small general store. A black dog was lying down on the doorstep. Gus raised his weapon and lined the dog up, but before he could shoot, the shopkeeper came out.

"'No one owns this dog,' she said.

"Gus repositioned himself and killed the dog with a single shot. The lady lowered her head and went back inside without speaking another word. The dog was quickly bagged and put onto a motorbike and we drove off."