Thirty years on from the attack on Brian Stack, Sinn Féin leader Gerry Adams has expressed his "regret" to the victim's family over the killing.
The father-of-three, then chief prison officer at Portlaoise Prison, was shot in the back of the neck on March 25, 1983, on a busy Dublin street as he left a boxing contest at the National Stadium.
Paralysed and brain-damaged from the shooting, he suffered for a further 18 months before dying from his injuries at the age of 47.
His sons Austin, who is assistant governor of Dublin's Wheatfield Prison, and Oliver had met with the Sinn Féin leader in May, where they urged him to put pressure on republicans to reveal what they knew about the killing.
Mr Adams accompanied them to a meeting with a former IRA leader who had enquired into the events surrounding Mr Stack's murder.
The prison officer's sons were driven to a bungalow at an undisclosed location in a blacked out van from Dublin's M1 motorway, where they were handed a statement, printed up on a typewriter, and told to transcribe it.
Some years later, when the army council discovered that its volunteers had shot prison officer Brian Stack, the volunteer responsible for the instruction was disciplined.
The statement said: "Prison officers were killed by the IRA in the north. These killings were sanctioned by the IRA leadership but none were sanctioned in the south and none was asked for in the case of your father.
"In Portlaoise a brutal prison regime saw prisoners and their families suffer greatly. This is the context in which IRA volunteers shot your father.
"This action was not authorised by the IRA leadership and for this reason the IRA denied any involvement."
The statement said the IRA killers involved were acting under orders and that the IRA was responsible.
"This operation should not have taken place," the statement continued. "While the IRA can no longer comment on this matter let me express my sorrow for the pain and hurt your family suffered."
On behalf of Sinn Féin I extend my regret at the killing of Brian.
Gerry Adams, Sinn Féin leader
Commenting on Friday, Mr Adams said: "At the beginning of May I met Austin and Oliver Stack.
"They asked for my assistance in seeking answers and closure to questions they have surrounding the killing of their father. I told them I would try to help.
"Since then I have been working with Austin and Oliver to establish whether the IRA was involved in their father's death."
Mr Adams continued: "I want to pay tribute to the Stack family - to Sheila Stack and her sons, Austin, Kieran and Oliver.
He added: "I hope that these recent developments will help them achieve the closure they have sought for 30 years."
Austin Stack had said previously he believed his father was killed as an act of "vengeance and frustration" by the IRA because of his father's strict security regime at Portlaoise Prison, which housed all republican prisoners in the Irish State.
He said his father was also aware of plans for an IRA prison escape - which was later botched - and suspected insiders were helping the Provos.
Louth TD Mr Adams continued: "Addressing complex and painful legacy issues is an enormous challenge.
"Dealing with the human consequences of conflict in terms acceptable to victims and their families is very difficult, especially in the absence of a process which provides for the voluntary participation of witnesses.
"Nonetheless it is a challenge which republicans will not shy away from.
"This generation of republican activists who lived through and survived the war have a duty and a responsibility to do our best to help victims and families."
Tom Elliott of the UUP said: "Once again the IRA have proved their words are not worthy of belief and that they are strangers to the truth. Today's admission of guilt is further proof that you simply cannot believe a word the IRA say.
"Having lied for 30 years regarding the murder of Mr Stack, one has to ask how anyone could believe anything the IRA might say regarding other terrorist acts they committed."
|Prison officer Brian Stack, who was murdered by the IRA in 1983.|