A woman and her boyfriend have been arrested in the American Pacific Northwest after the Christmas Eve killings of three generations of her family.

Six people were shot in an apparent row over money at a single-storey wooden house at the end of an untarred road in Carnation, a rural town of 2,000 about 20 miles from Seattle.

The victims included the woman’s parents, her older brother and his wife, and their two young children.

Michele Anderson and Joseph McEnroe, both 29, who lived in a caravan on an adjacent piece of land owned by her parents, were taken into custody by police when they visited the crime scene on Wednesday.

The victims were identified as Wayne Anderson, 60, a Boeing engineer, and his wife, Judy, 61, a postwoman, who lived on the property; their son, Scott, and daughter-in-law, Erica, both 32; and their two grand-children, Olivia, 6, and Nathan, 3, who were visiting for Christmas Eve. Ben Anderson, a grandson of Wayne and Judy Anderson, told reporters outside the home that his aunt, Ms Anderson, and her boyfriend, Mr McEnroe, had admitted to the killings.

“It was just money. She had a different way of thinking,” he said. “My grandparents had a lot of money. She had lived on the property rent-free her whole life, and they were just trying to help her out. She felt she wasn’t loved enough and everyone didn’t appreciate her and she was pushed out of everyone’s life,” he said from his car, after dropping off a wreath.

Police were struggling yesterday to explain why officers had not intervened when they received an emergency call from the house at 5.13pm on Monday. Nobody spoke to the operator and the call was disconnected after about ten seconds. The police dispatcher noted: “Heard a lot of yelling in the background. Sounded more like party noise than angry, heated arguing.”

Police officers were sent to the property at 5.19pm to investigate and arrived at 5.45pm but stopped at a locked gate, from which they could not see the house.

Sergeant John Urquhart, a police spokesman, could not explain why the officers had failed to determine who had made the emergency call, as required by department policy. But he insisted that the call appeared to have been made near the end of the killing spree and that the police would not have been able to prevent it.

The massacre was finally discovered at 8am on Wednesday, when a postal worker went to the house to check up on Mrs Anderson after she failed to turn up for work. As police swarmed to the crime scene, Ms Anderson and her boyfriend walked over from their next-door home and were arrested.

In court papers, the police alleged yesterday that the couple admitted the crime and went to her parents’ home intending to kill them both. The police said Michele shot her father with a 9mm handgun and Mr McEnroe shot him with a .357 Magnum. Mr McEnroe then shot Michele’s mother twice. Soon afterwards, the court papers alleged, Scott Anderson and his family arrived. Police said both Ms Anderson and her boyfriend shot the two adults and Mr McEnroe shot the children. The suspects then allegedly dragged the bodies to a garden shed.

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