Police have released a picture of Michael Atherton, who killed three people in a shotgun rampage.
Atherton, 42, gunned down his partner, Susan McGoldrick, 47, her sister Alison Turnbull, 44, and niece Tanya Turnbull, 22, on New Year's Day at their home in Greenside Avenue, Peterlee, Co Durham, before shooting himself.
Police believe Atherton and McGoldrick were out drinking in different venues that evening. They returned to the house together and argued. Atherton pulled out a shotgun and opened fire.
McGoldrick was shot in the kitchen, while the Turnbulls were both killed in the living room. After the attack, which is thought to have taken seconds, Atherton took his own life.
Another woman, thought to be 19-year-old Laura McGoldrick, escaped the massacre by leaping from a window. She was hit by shotgun pellets in the wrist and shoulder, before raising the alarm by banging on neighbours' doors.
Police confirmed that there were other people in the house at the time of the shootings. It was also confirmed that the shotgun used was registered to Atherton, who owned six licensed firearms.
The Independent Police Complaints Commission has launched an investigation into the police decision not to revoke Atherton's licence despite officers being called to an incident in 2008 when he threatened to harm himself.
"My officers are continuing to work closely with the victims' families to piece together the series of events that led to this tragic incident and to establish a motive," said senior investigating officer Det Supt Paul Goundry.
"It appears a family argument took place immediately prior to the shootings and we are determined to leave no stone unturned in our bid to find out exactly what happened.
"We will continue to pursue all lines of enquiry and work closely with all relevant partnership agencies. This will help us develop the clearest picture we can of the tragic events."