ROME, Italy — When 79-year-old Sister Bernadetta Boggian, of the Xaverian order, called Father Mario Pulcini on Sunday afternoon to tell him that she had just discovered two of her elderly colleagues brutally raped and murdered in their convent in Bujumbura, the capital of Burundi, she had no idea she would face the same fate just nine hours later.

Instead, the elderly nun guided Father Pulcini through the carnage, past the pools of blood, first to Sister Lucia Pulici, 82, who was lying on the floor with her throat cut, and then to Sister Olga Raschietti, 75, whose head had been smashed with a rock.

“The police came. They took the bodies to the morgue and the four remaining sisters went to their rooms to rest,” Pulcini told Italy’s La Repubblica newspaper, adding that witnesses saw a man running away from the scene with a knife in his hand. “I insisted that they not spend the night in the convent, but they wouldn’t listen to me.”

Around 2 o’clock Monday morning, the priest, who lived with the male missionaries just 40 meters away, got another call from the convent.

“I was awake, trying to write the details of the brutal double homicide for my superiors, when a sister called to say, ‘The murderer is still here,’” he said, explaining that the nun had heard noises and she and two other sisters were hiding in their rooms.

Pulcini had locked the front door of the convent, but now he found it open. “By then, Bernadetta was in her room, dead,” he said. She had been raped and beaten before being decapitated. Apparently the man who fled had not been alone. An accomplice had stayed behind.

What could provoke such extraordinary brutality? For once, religious and ethnic motives may not have played a role. Instead, a more primal fury may have driven the killers. The mission’s main goal was to provide support to children, female victims of domestic violence, and the mentally ill. According to local press reports, the motive was not likely a botched burglary, as is being reported in Italy, since money and valuable religious artifacts made of silver were not taken from the house. Detectives in Burundi reportedly have questioned at least three men whose wives were cared for and protected by the nuns after incidents of domestic violence and who may have killed the nuns out of revenge.

The three nuns were no strangers to working in Africa’s difficult, sometimes hostile environments. According to the diocese of Parma, Italy, where the Xaverian order is based, they had all faced challenges working in Zaire, now the Democratic Republic of Congo, in the 1970s and 1980s.

Raschietti had worked in Africa for more than 50 years. Pulici, who had been in Burundi since 2007, was in ill health and no longer worked but had chosen to stay in the convent to offer prayers in support of the other missionaries.

In 2007, Boggian left the Congo for Burundi after a brief time back in Italy. In a letter she wrote a year ago she said, “At this point in my journey I continue my service to our African brothers, trying to live with love, simplicity and joy.”

The Italian missionary spokesman in Parma has denied reports that the elderly women were victims of sexual violence, but Burundi police spokesman Colonel Helmegilde Harimenshi and Father Pulcini both said they had been raped before they were beaten and killed with a knife.

The Vatican said Pope Francis felt “great sadness” over the killings, which are not, at the moment, considered to be motivated by anti-Christian sentiment. He said he hoped their “shed blood [would] act as a seed of hope in order to build authentic brotherhood among peoples.”

In 1995, two Italian priests and a female lay volunteer with the same Xaverian mission were murdered in Burundi after being accused by then-dictator Jean Baptiste Bagaza of backing the Hutu militia. This was in the wake of the genocidal Hutu-Tutsi war in neighboring Rwanda.

Bagaza called for the expulsion of all Italian priests and missionary workers, but those who stayed received death threats. The three who were killed had been forced to kneel in a prayer position while assassins shot each in the forehead. The female worker was additionally shot through the heart. Their deaths eventually were blamed on Hutu extremists. In 2011, a Croatian nun working in an Italian charity in Burundi was killed during an attempted robbery.

Full autopsies on the three nuns may not be completed, according to a spokesperson with the Burundi embassy in Rome, who said the Italian government was not asking for autopsies at this point, and who implied their causes of death are apparent enough not to investigate more. So the question of rape may not be resolved.

Italian Foreign Minister Federica Mogherini described her “great pain” over the murders. “We’re once again witness to the sacrifices made by those who, with complete dedication, spend their entire lives relieving the overwhelming suffering that still exists in Africa,” she said in a statement. The women are expected to be buried in a cemetery in the convent in Bujumbura.