Ulster Defence Association (UDA) member, John Boreland, who was in his mid-forties, was gunned down in Sunningdale Gardens, in the unionist Ballysillan area of north Belfast, at 9.50pm on Sunday.
Two years ago, the victim, who was linked with local criminality, was shot in the thigh by rival loyalists. The killing has prompted fears of an escalation of violence between loyalist factions.
First Minister, Arlene Foster, Deputy First Minister, Martin McGuinness, and Northern Ireland Secretary, James Brokenshire, have all condemned the killing.
“Shocked and disgusted to hear of a murder in Belfast tonight,” Mrs Foster tweeted.
“I urge everyone to work with the police, as they investigate.”
Mr McGuinness branded the shooting “shameless”.
“There can be no justification for the murder of a well-known loyalist in N.Belfast tonight,” he tweeted.
“This was shameful & I unreservedly condemn it.”
Mr Brokenshire said on Twitter: “Concerned to hear of fatal shooting in N Belfast. No place for violence in communities. Urge anyone with info to contact PSNI.”
Ulster Unionist member of the Northern Ireland Policing Board, Ross Hussey, said: “I am very saddened to hear of a fatal shooting in north Belfast.
“Murder is murder and cannot be justified. It must be condemned.
“I would urge anyone with information to contact the police, so that those responsible can be brought to justice.”
There have been mounting tensions between rival loyalists in north Belfast in recent weeks.
Loyalist gunmen have been responsible for dozens of murders since the organisations supposedly went on ceasefire in the 1990s.
Many of the killings have been linked to feuds and turf wars among loyalist rivals.
The latest shooting has prompted further questions about the authenticity of the ceasefires.
Last year, the main loyalist paramilitary groups restated their commitment to non-violence, as they came together to launch a new initiative, the Loyalist Communities Council.
Boreland was a close associate of well-known north Belfast loyalist, Andre Shoukri.