A man shot twice with a shotgun was found dead on his kitchen floor, police have said.
Farmer David Murphy, 52, was discovered by a friend on Tuesday afternoon at his home where he lived alone on the outskirts of Ballymena in Co Antrim.
Police forensics officers combed the back of the house for clues on Wednesday.
The victim was known to police and detectives said his background would form part of their investigation to consider whether it was relevant.
Detective Superintendent Jason Murphy said: “David Murphy was at home, he was alone, he felt he was safe in his house and was entitled to feel that he was safe in his house.
“Someone decided deliberately to go to his house and fire shots at him, killing him in his house when he should be at his safest.
“That for me is indicative of the level of brutality here that we are talking about in terms of this offence.”
Police launched a murder investigation on Tuesday evening.
Forensic investigators have been examining the house in Church Road, Glenwherry.
Detectives want to trace Mr Murphy’s movements between Saturday and Tuesday lunchtime.
Mr Murphy added: “We are trying to ask people to help us fill some of those gaps about who David was with and whether members of the public can themselves suggest any motive for why anyone would have wanted to do him any harm.”
Several lines of inquiry are being processed and the senior officer said it was too early to have a clear idea about the motive.
He appealed for members of the public in the area of Church Road with dashcams on their vehicles or who may have noticed anything to come forward.
Alliance MLA Stewart Dickson condemned the attack.
“This is a shocking incident and my thoughts are with the loved ones of the deceased at what must be an extremely sad time for them,” he said.
“It will have caused great distress in what is a quiet rural area.”
Sinn Fein’s Oliver McMullan said the local community was in shock.
“This is a quiet area and locals are alarmed at what has happened,” he said.
The SDLP’s Declan O’Loan said: “The lesson is that these shadowy forces who wreak such havoc need to be rooted out of our society.”