A man and woman in their forties were shot dead in Belfast in the early hours of yesterday in a domestic row that boiled over into horrific violence.
A 15-year-old girl, a daughter of the dead woman from a previous relationship, was also shot and is now recovering in hospital after emergency surgery.
The injured teenager's brother (21), was also in the house, in a quiet area of east Belfast, at the time but was not injured.
The dead were named last night as Mr Brian Smith (47), and his partner Ms Mary Crilly (40).
Mr Smith was a former prison officer at Magilligan jail in Co Derry.
He retired earlier this year and could have had legal access to a personal protection weapon.
Murder squad officers said they did not suspect paramilitary involvement nor any connection with drugs or organised crime. They are not looking for anyone else in connection with the deaths.
The PSNI was unable to say whether one or more guns was involved in the shootings or to suggest who fired the fatal shots.
The dead couple had recently moved to Hills Avenue. A neighbour said: "A taxi driver told me there was a blazing row at the house last night." Mr Kenneth Keenan, a next-door neighbour, said he heard blasts but mistook the shots for fireworks.
"Last night with the squibs going off for Hallowe'en I heard a couple of shots. But it could have been squibs.
"When we came out the police were everywhere. It's unbelievable. You are living next door to it and you didn't know." Mr David Ervine, the Progressive Unionist leader and an East Belfast Assembly member said: "It's horrific stuff. Maybe we will never know the answers to what was going on in somebody's mind that causes such an outcome."
Ulster Unionist councillor Mr Jim Rodgers said residents could not believe what had happened.
"This is a dreadful tragedy and my thoughts and prayers are with the family circle at this sad and difficult time," he said.
"Hills Avenue is a quiet cul-de-sac and in visiting the scene this morning, people . . . were shocked and stunned at hearing this terrible news."
As PSNI forensic experts examined the scene of the shooting yesterday, Supt Alan Mains confirmed a number of shots had been fired in the house.
"We are looking at the containment of the house itself, that's where the investigation is focusing," he said.
"You often go to scenes, one like this morning, where a family has been basically devastated. To me it's meaningless," he said.