Gardaí investigating the murder of leading drug dealer Martin "Marlo" Hyland are satisfied he was killed by one of his own gang following an implosion in the gang's structure in recent months.
Gardaí say while the investigation into his murder, and that of plumber's apprentice Anthony Campbell, is at a very early stage, they believe Hyland was not killed by a rival gang.
Mr Campbell's family yesterday said they doubted if his killers would ever be brought to justice.
Minister for Justice Michael McDowell said while he could not guarantee a successful outcome to the investigation, everything possible was being done to bring about such a conclusion.
He said Mr Campbell (20), of St Michan's House, Dublin, was killed by "evil, savage people" who decided to kill him "for convenience" because he was a potential eyewitness to the Hyland murder.
"It is a really shocking thing that must simply destroy that family," he said of the Campbells. He was shocked by the 20-year-old's killing, describing him as a "model" young man who was "completely innocent".
Gardaí investigating the double murder on Tuesday morning at Scribblestown Park, Finglas, yesterday set up checkpoints on main roads in Finglas and Glasnevin in the hope that passing motorists may have seen something suspicious around the time of the murders.
They are particularly anxious to talk to anybody who may have seen the getaway vehicle, a black Volkswagen Passat, registration 06 D 27432, which was found burned out in Ballygall, Glasnevin.
It was stolen in the midlands on November 30th and gardaí want to talk to anybody who may have seen it since then.
Detectives now suspect the involvement in the murders of a close associate of Hyland's who had become unhappy about the way he was running his drugs empire and particularly the unprecedented level of Garda scrutiny he had been attracting of late.
Hyland (39) had emerged in the last two to three years as one the biggest drug dealers in the country.
He had also ordered two recent gangland-style murders and was implicated in helping a foreign national who is suspected of organising the killing of Latvian mother-of-two Baiba Saulite (28) in Swords, Co Dublin, last month.
He had found himself at the centre of one of the biggest gangland investigations since the 1996 murder of Veronica Guerin in the shape of the recently established Operation Oak.
It involved members of every specialist Garda unit and was the priority investigation for the organised crime unit within the National Bureau of Criminal Investigation.
Operation Oak has resulted in the seizure of drugs worth an estimated €15 million and the arrest of 30 criminals who worked for Hyland or were associated with him. Many are currently facing serious criminal charges relating to drugs and weapons finds.
Gardaí are now working on the theory that the control he enjoyed over his large group of associates and his drug-dealing activities had slipped as the Garda investigation into those activities heightened recently.
A list of suspects has been drawn up with one man emerging as the chief suspect. Many on the list are Finglas-based career criminals who are well positioned to fill the power vacuum in the drugs trade created by Hyland's murder.
Postmortems on the remains of the victims were concluded late on Monday night and revealed they had both been shot in the head.
Mr Campbell was shot once while Hyland was riddled with six bullets. He was shot twice in the head and four times in the upper body as he lay in bed. The bodies of both victims were identified by their families yesterday.
Anybody with information on the killings is asked to contact Finglas Garda station on (01) 6667500.