Editor’s note: The images below may be upsetting to some readers.

When photographer Paul Hilton arrived at a clearing in Sumatra, Indonesia, last year, there was just a backhoe, a couple of law enforcement officials and an open pit about to be set on fire ― the final act of a major wildlife crime bust.

The day before, Hilton had been in a warehouse in the city of Medan when police raided the building on a tip that a seafood trading company was trafficking in smuggled creatures hunted for their valuable body parts. He photographed the raid and the lucky critters that made it out alive. Though he found it heartbreaking, “visually, it wasn’t that impactful,” Hilton said.

But it was the pit a few miles away that made it hard to lift his camera. The warehouse had been hiding boxes, crates and shipping containers full of frozen pangolins, the world’s most trafficked animal, destined for consumption abroad.

The trench Hilton strode up to that day was a mass grave, filled with nearly 4,000 pangolins that the authorities had seized from the seafood company.

“I stood there for a while and I couldn’t even take a photograph,” said Hilton, who was on assignment for the Wildlife Conservation Society at the time. “It was the early morning, a very stark landscape with just a few police officers. And I’m just standing there looking into this pit thinking, ‘What an absolute disgrace.’”

Credit: Paul Hilton/Wildlife Photographer of the Year Awards Paul Hilton's prize winning photograph, titled "The Pangolin Pit," shot after the raid.

One of Hilton’s photographs from that day, above, won first prize in the single image category at the Wildlife Photographer of the Year awards last month. It’s a stark and depressing shot that reflects the dire struggle pangolins face as humans hunt them to extinction.

Pangolin scales are highly prized in traditional medicine and the meat is considered a delicacy in some parts of Vietnam and China. Like rhino horn, the scales are made of keratin, the same material as human fingernails, and hold no medicinal value whatsoever.

But demand for pangolin parts is staggering, and all eight species across southeast Asia and Africa are threatened by poaching. More than 10,000 of the animals are estimated to be killed every year. Hilton said in some areas the scales can sell for up to $600 a kilogram.

The pangolins Hilton photographed that day were worth an estimated $1.8 million.

The Convention on International Trade in Endangered Species of Wild Fauna and Flora, or CITES, recently banned the trade of pangolins and their parts in an effort to squelch demand.

Hilton’s photographs from the raid and the burn pit show just how vast the wildlife trade can be, and how easy it is for one species ― humans ― to eat one of the world’s mammals to extinction.

Take a look below.

Eaten To The Brink Of Extinction Credit: Paul Hilton/WCS The frozen bodies of 3,000 to 4,000 pangolins lying in a pit before being burned in Medan, Indonesia.

Credit: Paul Hilton/WCS

Credit: Paul Hilton/WCS Fire engulfs thousands of frozen pangolins in a pit dug outside Medan, Indonesia.

Credit Paul Hilton

Credit: Paul Hilton/WCS Pangolin scales are prized as traditional medicine in parts of Asia.

Credit: Paul Hilton/WCS Frozen pangolins and scales are displayed during a pangolin bust in April 2015.

Credit: Paul Hilton/WCS An estimated 3.4 tons of pangolin parts were confiscated during the bust, with a street value of nearly $1.4 million.

Credit: Paul Hilton/WCS

Credit: Paul Hilton/WCS

Credit: Paul Hilton/WCS

Credit: Paul Hilton/WCS Nearly 100 living pangolins also were seized in the raids.

Credit: Paul Hilton/WCS The animals were found in cramped poultry cages.

Credit: Paul Hilton/WCS Wildlife officials released the surviving animals back into the wild following the bust.

Credit: Paul Hilton/WCS A baby pangolin and its mother.