Warning: This article contains graphic details.

A British crocodile expert was sentenced Thursday to more than 10 years in prison in Australia after admitting to sexually abusing, torturing and killing dozens of dogs.

Adam Britton, 53, a prominent zoologist who had worked with the BBC and National Geographic before his arrest in 2022, had pleaded guilty last September to dozens of bestiality and aggravated animal cruelty charges as well as the possession of child abuse material.

He filmed videos of himself torturing dogs to death and then shared the videos online under pseudonyms, the Supreme Court of the Northern Territory in Australia heard.

From November 2020 to April 2022, Britton sourced 42 dogs of varying ages and breeds, which he “tortured and sexually exploited for his own sadistic pleasure,” court documents said. At least 39 of the dogs were intentionally killed.

Chief Justice Michael Grant had warned those in the courtroom at an earlier hearing that the details of Britton’s crimes were so “grotesque” that they could cause “nervous shock,” the BBC and Australian media reported.

The “unalloyed pleasure” Britton took in torturing the animals was “sickeningly evident,” the BBC quoted Grant as saying.

In a handwritten letter his lawyer read out to the court on Thursday, Britton said he took “full responsibility for the demeaning crimes” he had committed against the dogs.

“I deeply regret the pain and trauma that I caused to innocent animals,” he said in the letter, which was dated July 16 and seen by NBC News.

The zoologist told the court he was suffering from a mental disorder that caused intense, atypical sexual interests that could be harmful to others.

“I now acknowledge that I’ve been fighting a rare paraphilic disorder for much of my life,” he said, “and that shame and fear prevented me from seeking the proper help I needed.”

Britton added he would seek long-term treatment.

Britton grew up in Britain before moving to Australia about two decades ago to work with crocodiles. He built a reputation around his expertise in zoology and appeared alongside the renowned British naturalist and broadcaster David Attenborough while working on a BBC documentary series.

According to the court documents, Britton sexually abused his own pets, Ursa and Bolt, for years but sought out other dogs as well.

“My own dogs are family and I have limits,” he said in a Telegram message cited in the documents.

He targeted people online who were re-homing their pets, building a “rapport” with them and persuading them that he would take good care of them. Instead, he kept them in a shipping container on his property that was filled with recording equipment and that he called his “torture room.”

When the dogs’ former owners asked about them, Britton would send them old photos from before he started torturing them when in some cases they were already dead.

Britton’s crimes, which are estimated to have begun in 2014, went unnoticed until April 2022, when police executed a search warrant at his home outside the Australian city of Darwin. They had received an anonymous tip about an online video of dogs being tortured in which a bright orange City of Darwin dog leash was visible in the background.

Britton has been in custody ever since the search, during which police seized 44 items including sex toys, dog paraphernalia, cameras and weapons. They also found severed dog parts and bodies.

Britton was sentenced to 10 years and 5 months in prison, including time served. He will be eligible for parole in 2028, the court told NBC News, adding that he is banned from owning any mammals for the rest of his life.

Animal rights advocates speaking outside court on Thursday said Britton’s sentence was insufficient and that penalties for animal cruelty should be increased.