After being repeatedly slashed with knives, Rumbali's older sister and two teenage nieces were released following negotiations with police. Rumbali, a 40-something former schoolteacher, was beheaded.
Her assailants claimed they had clear proof that Rumbali had used sorcery to kill another villager who recently died of sickness: The victim's grave bore the marks of black magic, and a swarm of fire flies apparently led witch hunters to Rumbali's home.
Violence linked to witch hunts is an increasingly visible problem in Papua New Guinea a diverse tribal society of more than 800 languages and 7 million people who are mostly subsistence farmers. Experts say witch hunting appears to be spreading to parts of the country where the ruthless practices never took place before.
There is no clear explanation for the apparent uptick in killings in parts of the South Pacific nation, and even government officials seem at a loss to say why this is happening. Some are arguing the recent violence is fueled not by the nation's widespread belief in black magic but instead by economic jealousy born of a mining boom that has widened the country's economic divide and pitted the haves against the have-nots.
"Jealousy is causing a lot of hatred," said Helen Hakena, chairwoman of the North Bougainville Human Rights Committee, which is based in the area Rumbali was killed. "People who are so jealous of those who are doing well in life, they resort to what our people believe in, sorcery, to kill them, to stop them continuing their own development."
She said the witchcraft accusation against Rumbali was just an excuse.
"That was definitely a case of jealousy because her family is really quite well off," Hakena said.
She said villagers were envious because Rumbali's husband and son had government jobs, they had a "permanent house" made of wood, and the family had tertiary educations and high social standing.
The United Nations has documented hundreds of cases of sorcery-related violence in Papua New Guinea in recent years and many more cases in remote areas are thought to have gone unreported. It found the attacks are often carried out with impunity.
Until last month, the country's 42-year-old Sorcery Act allowed for a belief in black magic to be used as a partial legal defense for killing someone suspected of inflicting harm through sorcery. The government repealed the law in response to the recent violence.
"There's no doubt that there are really genuine beliefs there and in some circumstances that is what is motivating people: the belief that if they don't kill this person, then this person is going to continue to bring death and misfortune and sickness on their village," said Miranda Forsyth, a lawyer at Australian National University who has studied the issue.
But she said recent cases in Papua New Guinea don't appear to be motivated by a genuine belief in the occult, but instead are a pretext under which the wealthy can be attacked by poorer neighbors, and, many times, get away with it.
She and other experts on witchcraft in the Melanesia region believe Papua New Guinea's newfound prosperity and the growing inequality in its traditionally egalitarian culture is a significant cause of the violence. Neighboring Vanuatu and the Solomon Islands, where belief in black magic is also widespread, haven't seen the same level of extreme violence against accused witches.
The difference, they say, is that Papua New Guinea has had the fastest economic growth.
A wealth of mineral resources and natural gas has transformed the nation's long-stagnant economy into one of the world's fastest growing over the past decade, increasing on average almost 7 percent annually from 2007 to 2010. Growth peaked at 8.9 percent in 2011 before slowing to 8 percent last year.
The Asian Development Bank reported last year that Papua New Guinea has one of the highest levels of inequality, if not the highest, in the Asia-Pacific region.
These socio-economic problems have inevitably played into a cultural landscape that includes a belief in witches and black magic, said Kate Schuetze, a regional researcher for Amnesty International.
"There is always a reason for the accusation, whether it's jealousy, wanting to access someone else's land, a personal grudge against that person or a previous land dispute," Schuetze said.
Papua New Guinea Deputy Public Prosecutor Ravunama Auka doesn't buy that jealousy has been behind a significant number of the sorcery-related slayings he had dealt with. While he did not have statistics, he said most victims were slain due to a genuine belief that they had killed through sorcery.
Auka had no doubt sorcery-related slayings were increasing, but could not explain why.
"There are all sorts of reasons, not only because some people are wealthy and some are not," Auka said.
Another possible explanation is the spread of particularly vicious sorcery beliefs that before were just seen in the highland province of Chimbu, said anthropologist Philip Gibbs, a sorcery specialist and Roman Catholic priest who has lived in the wilds of Papua New Guinea for the past 41 years.
In Chimbu, people bury their dead in concrete so that the bodies will not be eaten at night by small demonic animals that they believe can possess the living. Villagers pay witch doctors to divine who among them are possessed by these demons, which they believe leave the person's body at night and take on the form of any small animal.
Gibbs said those suspected of being possessed are often tortured to make confessions and are sometimes killed.
"That form is spreading to other provinces where it's never existed before and we're asking the question why," Gibbs said.
Accused families abandon their small farms in a hurry, usually taking only what they can carry in a bag. The villagers must then decide who occupies the vacant land.
"That's where the jealousy and the greed can come in," Gibbs said.
Papua New Guinea is under growing international pressure to respond to the violence after a series of high-profile cases made world headlines.
In February, a mob stripped, tortured and bound a woman accused of witchcraft, then burned her alive in front of hundreds of horrified witnesses in Mount Hagan, the country's third largest city. In July, police arrested 29 people accused of being part of a cannibal cult in Papua New Guinea's jungle interior and charged them with the murders of seven suspected witch doctors.
In the case of Rumbali, which took place in April, no arrests have been made, but police said they are treating it as "first degree murder."
Police Senior Inspector Cletus Tsien would not speculate on the motive for the crime.
"We know that this family was wealthy. We know that maybe there were bits and pieces of jealousy. We know they were accused of sorcery ... but there's no concrete evidence as to which factor contributed to the death of the late woman," Tsien said.