With fear etched on his face, a man kneels on the ground, hands tied. Three masked men stand over him, one pressing a revolver to his head, another resting a huge axe on his skull, the third brandishing a machete.

Next to him lies the battered and bloodied corpse of another man.

“Why do you steal from us?” asks a voice behind the camera. The man, knowing he’s about to be killed too, ­defiantly replies: “Because I’m a pirate.”

This video, filmed by drug traffickers who caught a group of raiders, shocked locals in Coari on the Amazon river.

And it laid bare for the first time the murderous world of the modern pirates who terrorise this ­dangerous stretch of the world’s longest waterway.

The gangs made headlines this week when British canoeist Emma Kelty, 43, was ambushed, robbed and murdered on a 4,000-mile solo trip along the river.

Emma Kelty was murdered as she paddled along the Amazon in a canoe (
Image:
Facebook)

The beach where she camped, – halfway along an 84-mile stretch between the towns of Coari and Codajas – is in the heart of pirate territory.

Seven members of the Water Pirates group are believed to have shot and stabbed the former headteacher, of Finchley, North West London, before dumping her body in the murky water.

Suspected leader Evanilson Gomes da Costa, 24, has since been killed, possibly by another gang.

Three were arrested and three are still being hunted.

But for locals, being ­attacked by the criminals, known as “water rats”, is a constant threat. Just last month, pirates attacked a motorised canoe and shot dead its occupants, believed to be Peruvian drug traffickers, in the exact spot where Ms Kelty was killed.

And in December, again in the same place, a police boat was ambushed.

Coari’s police chief, Thyago Garcez, vanished during the ensuing shootout.

Members of the gang involved in the murder of Emma Kelty (
Image:
Collect Unknown)

According to Achipo Goes, a blogger from Coari, pirates used to only attack boats carrying drugs on one of the main trafficking routes from Colombia. But now anybody is a target. He says: “Nobody is surprised the British woman was attacked and killed.

“She paddled in to pirate territory and camped alone on the side of the river. The pirates are bloodthirsty and cold, with a ­reputation for brutality.

“After they kill someone they often cut them open and remove their intestines, so their bodies don’t float when they throw them in the river.”

Once a rainforest wilderness where few made their home, the population of the Amazon has surged by 22% to nearly 25 million people in recent years.

But it is one of the poorest parts of Brazil, and organised crime thrives. In remote riverside villages, residents complain police boats rarely venture into the most crime-ridden areas.

Coari’s police chief, Thyago Garcez, vanished during a shootout with pirates

Armed with sophisticated weapons, the pirates ambush at night and in remote spots with no phone signal. They often attack ships using several speedboats before pillaging cargoes – and killing anyone who resists.

The most sought-after “treasure" is diesel, which is easily sold. This year pirates have raided the Petrobas oil terminal in Coari six times, exchanging fire with security guards.

But it is their involvement in drug-trafficking which has turned this part of the Amazon into one of the world’s most dangerous places. And with pirates often intercepting hauls worth millions of pounds, they have found themselves being hunted by one of Brazil’s most feared criminal factions, the Family of the North, or FDN.

In the video, which emerged last August, FDN members interrogate the doomed pirate identified as Ariomar Correa, 34. He is forced to give the names of his superiors and says the last stolen consignment was 160 kilos of cocaine , worth around £500,000.

The Coari lake lies is in pirate territory (
Image:
LightRocket)

Asked if it is worth being a pirate, he replies: “No, because pirates die, just like we are dying here.”

Correa’s body, like those of the three others, has never been found.

Retired Federal Police chief Mauro Sposito, however, believes powerful drugs cartels are more afraid of pirates than they are of police. He says: “The pirates attack craft transporting drugs, kill their occupants, then open up their stomachs and throw them in the river so they become fish food. They leave no tracks.”

But it is the violent attacks on local people which has left communities living in fear. Businessman Evandro da Silva, 53, was fatally stabbed and his wife beaten up in a raid on his riverside shop in June. A month earlier, Ricardo Costa, 42, was shot dead when his fishing boat was attacked.

Armed police patrol the Amazon river

In February two clergymen survived being shot as they arrived to give a Bible course at the Dom Bosco
riverside community, near Coari.

During another robbery, pirates stole all the belongings – including clothes – of 150 passengers on a riverboat travelling from Coari to Manaus.

With such a reputation for ruthlessness, it is no wonder locals tried to warn Emma, who died on Tuesday.

In a Facebook post days before her murder, she wrote: “So in or near coari (100km away) i will have my boat stolen and i will be killed too. Nice.”

Two days later she posted: “Am in the clear. All OK.” Unbeknown to her, she was paddling deeper into trouble.

matt.roper@mirror.co.uk