Murdered loyalist Alan McCullough was a military intelligence spy who double-crossed both factions of a feuding terror organisation, his killers claimed tonight.
As detectives continued to question a man about the murder, the Ulster Defence Association also accused McCullough of being heavily involved in four assassinations.
The paramilitary grouping provoked a wave of revulsion for killing McCullough, a former ally of ousted loyalist Johnny Adair, after apparently agreeing to lift a death sentence against him.
The 21-year-old fled to England after the UDA drove supporters of Adair's ruthless C Company unit out of Northern Ireland at the height of the internecine war.
But in a statement issued tonight the UDA claimed it wanted to set the record straight "once and for all".
It said: "Alan McCullough was an MI5 agent who "Judased" both the UDA and his murdering mates in C Company who were exiled from Northern Ireland.
"McCullough was military commander of the notorious, now defunct, C Company who gave the orders for four murders, numerous gun and bomb attacks and death threats throughout Northern Ireland."
A brutal power-struggle between Adair and his rival UDA commanders saw four men shot dead either side of the New Year.
Among those killed were the organisation's hardline South-East Antrim brigadier John "Grug" Gregg and his associate Robert Carson near Belfast docks.
As Adair languished behind bars, his supporters were forced to quit their Lower Shankill stronghold during a violent purge by mainstream UDA men out to avenge Gregg's death.
The organisation later called a 12-month ceasefire in a bid to restore its tattered image.
McCullough, C Company's military commander, only returned to his west Belfast home last month following negotiations with senior loyalists in the city.
Two weeks later, however, he vanished after being collected at his home by two of the UDA's top men.
A massive police hunt ended on Friday when a body found in a shallow grave in Newtownabbey, just outside north Belfast, was identified as the missing loyalist.
The UDA later admitted responsibility for the killing.
The 35-year-old man being questioned about McCullough's murder was later released without charge.
But detectives then rearrested him and accused him of being in possession of items likely to be of use to terrorists. He is due to appear before Belfast Magistrates Court tomorrow.
Another 33-year-old man was arrested tonight by detectives probing the murder, a police spokeswoman added.