Police in Northern Ireland are investigating the murder of a man who was found shot dead at his farmhouse in County Antrim on Tuesday.

A neighbour discovered the body of David Hugh Murphy, 52, a livestock farmer, at about 1pm at his home in Glenwherry, a village 20 miles north of Belfast.

Officers were at the scene and a postmortem will be held on Wednesday afternoon, DCI Geoff Boyce said in a statement.

There was speculation it was an internecine loyalist killing.

Murphy was convicted in 2004 of possessing firearms and ammunition for the Ulster Volunteer Force. Last year he and another man were charged with blackmail and threats to kill in relation to an alleged attempt to extort £10,000.

The Irish News reported that Murphy had been involved in an altercation with a group of men several days ago.

Politicians condemned the murder. Ian Paisley, the Democratic Unionist party (DUP) MP for North Antrim, said that part of his constituency was tranquil. “What has happened here has shattered that silence. There is no room for gun law in this society – there’s nothing justified about a man picking up a gun and taking a man’s life no matter what the circumstances are.”

Oliver McMullan, a former Sinn Féin assembly member, called for a thorough investigation into the circumstances from the weekend up to the time of Murphy’s death.

Declan O’Loan, a councillor with the Social Democratic and Labour party (SDLP), said: “The victim had a history of involvement in loyalist violence, and it seems likely that the motive for the murder lies in that arena.”

UVF members were blamed for a separate murder in Belfast last month. A gang beat and stabbed Ian Ogle, 45, a father-of-two and prominent loyalist, to death in front of his home.