A quiet neighborhood in northern Spain has been rocked by a killing so brutal it left even seasoned investigators shaken.

A 55-year-old woman was arrested Thursday in connection with the death of her longtime partner, a 67-year-old man found stabbed to death inside their apartment in Bilbao — with his genitals severed, according to Spanish media reports.

The killing occurred in the Uribarri neighborhood, where officers with the Ertzaintza responded to a call reporting a possible homicide on Jan. 30. Inside the residence, police discovered the man’s body showing signs of what authorities described as a “violent death.”

According to a translated police statement, the victim’s partner was present at the scene and allegedly confessed to the killing. She was taken into custody on suspicion of murder as investigators opened a formal inquiry into what led up to the attack.

Spanish outlet El Diario Vasco reported that the woman’s adult daughter contacted authorities after her mother told her she had committed the crime. The outlet further reported that the victim suffered multiple stab wounds, including to the neck, and that his penis had been cut off.

Neighbors told local media they heard shouting coming from the couple’s apartment prior to the killing, though no prior incidents had raised alarms in the building. Those who knew the pair described them as sociable and affectionate — a far cry from the violence that would unfold behind closed doors.

“They seemed like the perfect couple,” one neighbor told El Diario Vasco.

Another friend said she was struggling to comprehend what happened. “I’m in shock. We never expected this, and certainly not in the way it happened,” she said. “When I finished work, I would always have a beer or a moscato on the terrace with them. They talked, they laughed. There has to be something behind this.”

While police have not officially released a motive, El Diario Vasco reported that jealousy is being considered as a possible factor. Friends emphasized that there were no obvious signs of turmoil in the relationship.

“No one knows what happens inside people’s homes,” the friend added. “They seemed like a normal couple, not toxic at all.”

The couple had reportedly been together for five years. The victim was the owner of a local bar, well known in the area, which has only deepened the sense of disbelief rippling through the community.