Andrew Allen, 24, was blasted to death at his Buncrana home last as he lay on his bed with his girlfriend.
But now the top cop leading the investigation to find his killers said he believes the father-of-two did not believe he was in danger.
Mr Allen had moved from his native Derry after threats by Republican Action Against Drugs.
“He kept himself to himself and he never came to our attention.
“I have spoken to the family and they did not believe his life was in danger and that a previous threat had been lifted.
“If he believed there was a genuine threat he would not have been sleeping in the downstairs bedroom. There were many other secure rooms in the house,” Garda Supt Kevin English told the Shaun Doherty Show on Highland Radio.
The Buncrana-based Garda said it was “miraculous” that Mr Allen’s partner Arlene Farley was not shot.
“The events happened so quickly. It’s miraculous that Ms Farley did not receive any gunshot wounds.
“They knew exactly who were discharging their shots at. We are still are ballistic reports to say how many times he was hit,” added Supt English.
He appealed to anyone with any information on the murder to come forward to the Gardai or the PSNI in confidence.
“I don’t accept that these people can come in here and commit these crimes.
“They have no place in our society. They have been left behind by the democratic society. I would ask anybody with any information to come forward,” he said.
Meanwhile a march has been organised for today (SAT) in Derry to protest against the killing of Mr Allen.
“There is a deep anger amongst young Allen’s contemporaries and that will be borne out in the march,” said civil rights activist Eamonn McCann who is helping to organise the march.