Gangland criminal Mark Desmond may have been murdered in a revenge shooting by a gang who previously carried out a botched attempt on his life.
Desmond (41), who was known as the 'Guinea Pig', was gunned down in Griffeen Valley Park, Lucan, shortly before 8pm on Friday evening.
He was shot up to four times in the head before his killers fled in a Mazda vehicle.
The burned-out car was later discovered in nearby Hayden's Lane and a firearm was found in the vehicle's charred front seat.
A second gun was discovered nearby. Both weapons are now being forensically examined to determine if they were used in the murder.
A number of potential suspects have been identified by gardai as a result of Desmond's association with several gangs during his 20-year involvement in organised crime.
One of the main lines of inquiry is whether a gang who attempted to murder Desmond in 2010 are behind the murder.
During that incident in April 2010, three man approached the 'Guinea Pig' as he drove a quad bike in the Memorial Park, Ballyfermot.
Desmond noticed the group and fled the scene as at least one shot was fired at the thug.
Although this incident was never reported to gardai, officers identified the three men allegedly involved.
They included a notorious criminal from the Ballyfermot area who is now aged in his thirties, as well as a close associate of one of Mark Desmond's alleged victims.
Sources said that the Memorial Park shooting was ordered "at the behest" of this individual.
Gardai believe that Desmond was in the Lucan area last Friday evening to meet two brothers who are heavily involved in drug dealing.
Sources have revealed that he had met the siblings on several occasions in a number of premises in the Lucan area, and had been in contact with them since at least January of this year.
One of the brothers, who are originally from Clondalkin, has faced drugs-related charges in the past, but gardai have not been able to secure a significant conviction.
The two men are understood to have links to an organised crime gang based in Co Sligo.
It is believed that Desmond was followed to the crime summit by his killers, as opposed to being lured to his death.
The 'Guinea Pig' was chased from the Griffeen Glen area into the adjacent Griffeen Valley Park, before being shot up to four times in the head.
Desmond was suspected of involvement in at least four murders, as well as multiple beatings and sexual assaults, including the alleged rape of a 15-year-old boy.
The gun-for-hire was charged but never convicted of the horrific Canal Murders in 2000.
It is believed that Desmond lured Darren Carey (20) and Patrick Murray (19) to a meeting in Ballyfermot before murdering the two men.
Their bodies were then dumped into the Grand Canal, and were eventually discovered between January 9 and 10, 2000.
Desmond was also suspected of involvement in the murder of father-of-one James Kenny McDonagh (29) in 2009. His body was not recovered until January 2012, following an extensive search.
He was also a suspect in the 2009 murder of Anthony Cannon (26), one of jailed gang boss Brain Rattigan's key enforcers.