Esmond Bradley Martin, one of the world's top ivory investigators, has been murdered at his home in Nairobi.
The 75-year-old was found by his wife, Chryssee, at their home on the outskirts of Nairobi, having been stabbed in the neck.
Police are currently investigating the motive for his murder, with initial reports suggesting that the incident was an attempted robbery.
Esmond was known for his influential and groundbreaking work in tackling the global illegal ivory and rhino horn trade.
Having worked undercover in some of the world's most dangerous places, he had photographed and documented ivory markets, talked to traffickers and also calculated black market prices to help global conservation policy makers - often having to encounter gangsters and drug barons along the way.
Born in New York, Esmond first arrived in Kenya in the 1970s, when huge numbers of elephants were being killed for their tusks.
More recently, he had travelled to China, Vietnam and Laos with collaborator Lucy Vigne. Their research, funded by Save the Elephants, revealed that Laos has become the fastest-growing ivory market in the world.
They had also recently returned from an investigation in Myanmar, and Esmond was apparently writing up the date from the trip when he was killed.
His work in China has also been widely credited as fundamental to the recent ban of domestic ivory trade, as well as the sale of rhino horn in the 1990s.
Save the Elephants founder Iain Douglas-Hamilton said: "Esmond was one of conservation's great unsung heroes.
"His meticulous work into ivory and rhino horn markets was conducted often in some of the world's most remote and dangerous places and against intensely busy schedules that would have exhausted a man half his age.
"During his 18 years with Save The Elephants, Esmond - alongside his research partners - produced 10 crucial reports into legal and illegal ivory markets."
Bob Godec, US ambassador to Kenya, has said that Esmond's death is a tragedy not only for Kenya but also the world.
"His extraordinary research had a profound impact and advanced efforts to combat illegal wildlife trafficking across the planet," he said.
"African wildlife has lost a great friend, but Esmond's legacy in conservation will endure for years to come."
The BBC reports that the incident appears to have been a botched robbery, but also says that police are investigating whether it was linked to his work.
Last year 197 people were killed standing up to governments and companies that harm the environment or confiscate land, according to a recent report by Global Witness.
Featured Image Credit: Save the Elephants