KILLER cabbie Michael Atherton calmly walked out of his home after a “minor” row - and returned with a shotgun to coldly massacre his unsuspecting family.
As the shocking details were revealed, police also ruled out claims that Atherton suffered from depression which triggered the New Year’s Day slaughter.
Atherton gunned down his partner Susan McGoldrick, and her sister Alison Turnbull and niece Tanya Turnbull in a 10-second killing spree – before turning the gun on himself.
Speaking to the Mail lead investigator Detective Superintendent Paul Goundry said he believed the killings were a spontaneous act sparked by a “minor” row between him and other family members.
Det Supt Goundry said: “The argument was a minor domestic disagreement that involved Michael senior and other members of the family. There was a verbal dispute after which he left the house by the back door.
“There were no threats regarding him using any of his weapons, or to take anyone’s life.
“However, he re-appeared armed with a shotgun.
“He shot Susan first, then aimed at Alison and shot her. Then he shot Tanya, before turning the gun on himself.”
He added: “My investigations so far have found no evidence of Michael suffering from any form of mental illness or depression.
“It was his intention to go shooting the following morning with a friend, so this was not pre-planned, in my opinion.”
Laura McGoldrick and her step-brother, Michael junior, were inside the house at the time.
Michael escaped through the front door. Laura, who had been hit with spray when Atherton shot one of his other victims, and her boyfriend fled through an upstairs window.
A fourth woman, who was a friend of the three victims, was in the living room at the time of the shootings but was unhurt.
Det Supt Goundry said the firearms were kept in a secure cabinet in the main bedroom of the house.
Police said he was an avid shooting enthusiast and member of a local gun club.
An Independent Police Complaints Commission (IPCC) has been launched into the case after his guns were taken from him in 2008 over fears he could harm himself.
The guns were taken on September 10 after a family member called police, before they investigated the incident.
It has emerged Atherton wrote two letters to police asking for the guns to be returned during that period, but he was refused as officers were still looking into the matter.
They were returned on November 18 and he was sent a letter warning him about his future conduct and any repeats could see his licence revoked.
So far, there have been 50 officers working on the case, and Det Supt Goundry paid tribute to the Horden community for their support.
He added: “I would like to thank, from the bottom of my heart, the community of Horden and surrounding villages that have been involved in assisting my investigation.
“In particular, I would like to thank the residents of Greenside Avenue for their patience in allowing the forensic recovery from the house.”
Speaking about Laura and Michael junior, Det Supt Goundry went on: “They are an incredibly brave pair of young people.
“No-one can understand exactly what they have been through, but they have the love of the family around them in order to get them through this terrible time.”