By Mark Kinver
Science and nature reporter, BBC News
A female gorilla and its infant that were part of a 12-strong group attacked by gunmen last month are dead, say conservationists in the DR Congo.
The remains of the missing gorilla were found by patrolling rangers
Rangers patrolling the area of the Virunga National Park where four of the great apes were killed discovered the remains of the female, called Macibiri.
Conservation group WildlifeDirect said it would continue searching the area to locate the body of the infant, Ntaribi.
The latest casualties brings this year's gorilla death toll to nine.
Earlier this year, two silverback male gorillas were shot dead in the same area of the park in the north-east of the Democratic Republic of Congo, while a female was killed in May.
A census carried out in 2004 estimated that 380 mountain gorillas, more than half of the world's population, lived in the national park and surrounding Virunga volcanoes region.
The pair had been missing since the attack in July, which resulted in four members of the group, known to researchers as the Rugendo family, being shot dead.
At the time, conservationists in the area described the killings as "executions" because the bodies were left at the scene, whereas poachers would have sold the carcasses as either food or trophies.
Breaking the news on his Gorilla Protection blog on Thursday evening, WildlifeDirect's Paulin Ngobobo wrote: "Macibiri, the female adult who went missing the day of the attack, is dead.
"Just 20 minutes ago, the guards came back from their patrol with her remains.
"Her infant, Ntaribi - born 26 January of last year, has not been found. But now that the mother has been found, we are sure that the infant is dead too."
Robert Muir, project manager for the Frankfurt Zoological Society, said the news confirmed his worst fears.
"Seeing the bones being brought back today is equivalent to seeing the dead gorilla; it is a massive tragedy for everyone," he told BBC News.
"We had indeed hoped to find them alive; it is very sad that we have not."
The body of the 18-month-old infant has not been located, but Mr Muir said no-one held out any hope of finding it alive.
"It is just the case of finding the bones, or what is left of the baby's body, and bringing it back to the station for burial with the others.
"There is no way it would have survived without its mother."
As for the welfare of the remaining six members of the group, he said the gun attack was unprecedented and had left conservation groups uncertain about the family's future.
"We have absolutely no idea to how the family is going to respond. In the absence of a silverback (dominant male), the family unit has been destroyed.
"It is quite likely that a wild silverback will try to take over the group, which will cause a fair amount of stress for the family.
"But we just don't know because it has never happened before, we have never seen a family of mountain gorillas torn apart in this way."
The news comes on the same day that conservation groups launched an appeal to raise funds to increase the protection of the remaining gorillas.
The Zoological Society of London (ZSL), working with other organisations, has developed a three-month emergency action plan.
The strategy includes providing round-the-clock monitoring, increasing the number of patrols and funding an investigation into the July killings.
Dr Noelle Kumpel, ZSL's Bushmeats and Forests Conservation Programme Manager, said: "Shockingly, this is not the first time that gorillas in the park have been slaughtered in this way.
"We are calling on the public to support our appeal for funds to help us ensure that it does not happen again."