On October 4, a park ranger was killed in the Democratic Republic of Congo’s Kahuzi Biega national park while trying to protect the park’s rare Grauer’s gorillas.

The ranger, Munganga Nzonga Jacques, died at the age of 26. He was killed in the Tshivanga region of the park — an area that was previously believed to be safe for the gorillas, according to a statement by the Wildlife Conservation Society (WCS).

Jacques is the second ranger to be killed in Kahuzi Biega in the last six months. On 31 March 2016, rebel groups fatally shot another park ranger, Oscar Byamungu Mianziro, in Kahuzi Biega.

Munganga Nzonga Jacques died while trying to protect the park’s rare gorillas. Photograph: WCS

“We are very concerned about these increased threats to the rangers and their families and to the protection of these animals,” said Andrew Plumptre, WCS Senior Conservation Scientist for Africa, in a statement.

The Grauer’s gorilla — the world’s largest ape and a subspecies of the eastern gorilla found only in eastern Democratic Republic of Congo — is now facing an extremely high risk of extinction.

Wild gorilla numbers have declined by at least 77 percent over a single generation (~20 years), a recent study found, from an estimated 16,900 individuals in 1994 to about 3,800 animals now.

Their population collapse, which has resulted in up-listing of their status to Critically Endangered, is largely due to illegal hunting and civil unrest, conservationists say.

“The civil war in the Democratic Republic of Congo has led to the wide availability of arms and created a plethora of militia groups who control different territories in the east of the country,” Andrew Plumptre, senior conservation scientist for the Wildlife Conservation Society’s Africa Program, told PLoS One in an interview. “This has been terrible for conservation of its wildlife.”

Plumptre added that the civil war has resulted in an increase in artisanal mining sites deep inside the forests that are controlled by armed militias. These miners rely mostly on bush meat for food, and gorillas make an easy target.

Kahuzi Biega National Park is believed to be the last stronghold of grauer’s gorillas. So the murder of Jacques has conservationists worried about the future of the rangers as well as the gorillas.