The mother of Alan 'Bucky' McCullough last night branded his killers police informers.
Barbara McCullough made the claim after loyalist William 'Mo' Courtney was jailed last week for eight years over the killing.
Mrs McCullough insisted Courtney and others in the six-strong UDA gang were police agents.
The mum-of-six - who is set to meet the Police Ombudsman next week over her son's case - also plans to write a book about the case.
The Shankill woman's son, a pal of ousted terror boss Johnny Adair, was shot dead and buried in a shallow grave outside Belfast, in May 2003.
McCullough had fled Northern Ireland earlier, following the murder of UDA boss John 'Grug' Gregg, but returned after receiving assurances from Courtney that he would not be targeted.
Said Mrs McCullough: "It is our family's opinion that Mo Courtney was an agent of the state at the time of my son's murder, and also during the 1990s.
"But we also believe that some of the other UDA men who were involved in Alan's murder were police agents. We will inform Nuala O'Loan of everything we know and have learnt since 2003.
"We feel sorry for Courtney's family because he has lied to them all along. He told them a pack of lies and always said he would not be going to jail over Alan.
"UDA elements from north Belfast, west Belfast and south east Antrim were involved in the murder and we are determined to see them all in court. We even know who the gunman was.
"Courtney's plea shows that we have been telling the truth all along but this is not the end of it."
Courtney pleaded guilty to manslaughter after being cleared of murdering McCullough.