Last week rangers discovered the bones of a fifth victim, a female gorilla, Macibiri, that had been missing since the attack.
The rangers believe a carnivore had eaten the meat and dragged the bones away from the rest of the carcass.
Macibiri's infant, Ntaribi, is still missing and presumed dead.
"The baby was too young to survive alone when Macibiri was killed," said Innocent Mburanumwe, who is in charge of Virunga's gorilla monitoring.
"Ntaribi would have died of hunger if it was not killed by the murderers."
In the days after the attack, rangers were not able to get near the family's six surviving gorillas, some of which were injured.
"At the beginning they all just kept running away. But now they don't mind us being there," Mburanumwe said.
Among the gorillas killed was Senkwekwe, a male silverback and the group's leader.
The rangers hope that a solitary silverback will now take over the group, which includes three "blackbacks," male gorillas that are still too young to lead a family.
"But the main problem is there are no females of a reproductive age," Mburanumwe said.
"There's only one female, and she is too young to have babies. So we are very worried for the future of the family."
It is not known who massacred the gorillas, but conservationists believe the slaughter is linked to the burgeoning illegal charcoal trade in the park.
A joint team from UNESCO and the World Conservation Union (IUCN) has spent the past ten days in Congo investigating the killings.
Last week park rangers arrested some 50 women caught making charcoal inside the park. The women have since been released.
"They are victims," said Mushenzi, the park supervisor.
"We need to go up the chain where those in charge are brought to justice."
The "crisis cell" now patrolling the gorilla territory is part of an advance force normally stationed in northern Virunga, where hippo poaching is a major problem.
The upcoming permanent 50-person protection unit "is a crucial response to the emergency plan already initiated, as the problem [of the gorilla killings] may not be resolved immediately," said Lucy Fauveau, the Zoological Society of London's project manager for Congo in Goma.
Mushenzi, the park official in charge of gorilla-protection efforts, acknowledged that increasing patrols in the park may antagonize the gorilla killers.
"We have already received threats by phone in recent weeks as a result of our additional patrols, because we seek to end their illegal activities," he said.
Despite that, Mushenzi said, morale remains high among his men.
"I have the support of the rangers, and all the elements are there to succeed. We do not have a right to fail," he said.
"Would the gorillas be dead if they were not protected? Yes, they would. There are so many people who do not want this park to exist."
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