It was a gorilla massacre that shocked the world. Among the victims: the majestic silverback Senkekwe, his body riddled with gunshot wounds after a brutal execution; a female named Mburanumwe, killed with her unborn baby inside; and another, Safari, burnt to a cinder.
The rangers of Congo's Virunga National Park who bore the corpses of the rare apes on stretchers to be buried were visibly shaken by the wretched crime. Now it seems that some of them may have orchestrated the slaughter.
Honore Mashagiro, director of the park at the time of last year's atrocities, was arrested yesterday at his home in the eastern town of Goma on suspicion of arranging the killing of the endangered gorillas. Another six foresters are expected to be questioned in the coming days about trapping and killing the apes on the director's orders.
"This is a major breakthrough," said Dipesh Pabari, a spokesman for conservation group Wildlife Direct. "The Congolese authorities are showing the world that they will no longer tolerate mismanagement."
The slopes of the extinct volcanoes in Virunga, where the borders of Congo, Uganda and Rwanda meet, are protected by Unesco and are home to more than half of the 700 mountain gorillas not in captivity.
It was clear from the moment the bulk of the gorilla corpses were discovered, amid the forested slopes last July, that this was no ordinary killing. Local poachers were not suspected because the carcasses, potentially valuable on the bushmeat market, had been left behind. And a hit job for the trophy trade was ruled out as the animals still had their heads and hands.
"The people that did this located the animals in one go and they knew how to approach them, which suggests an inside job," said Dan Bucknell, the Africa programme manager for the Gorilla Organization.
Another prominent environmentalist sighed on hearing news of Mr Mashagiro's arrest: "He always seemed like one of the good ones."
The fact that Mr Mashagiro is also being investigated for illegal charcoal burning offers an insight into the likely motive for the gorilla killings. Illegal charcoal traders have been cutting down trees in the gorillas' habitat to fuel an industry thought to be worth around $30m (£15m) a year. But last year the Congolese government stepped up its attempts to clamp down on the illicit trade, and conservationists believe that this ruffled some feathers.
Mr Pabari said: "He [Mashagiro] was in a position of great responsibility, and allegedly used his authority to promote the destruction of forest for charcoal to make money. This threatened the gorilla habitat, so that when the rangers tried to protect the forest, he allegedly orchestrated the gorilla massacres to discourage them."
Mr Mashagiro, a senior official in the Congolese Nature Conservation Institute, was removed as director of Virunga not long after the killings and put in charge of the gorilla population at Kahuzi-Biega National Park.