Gardai believe that the man was lured to the area by his rivals -- associates of jailed gangster Christy Griffin.
The 41-year-old victim is a member of a group involved in a long-running dispute with Griffin's gang -- dubbed the Sheriff Street feud.
Tensions are high in the north inner city today amid fears of a revenge attack.
A source said: "It's a tinderbox situation and anything could set it off. Extra armed gardai have been placed in the area and mediation is under way.
"But things are very, very volatile. It had quietened down a bit in recent weeks but this has set if off again."
The gangland feud has already claimed five lives.
Angry relatives of the man are understood to have issued a number of threats after gathering at Beaumont Hospital after the shooting, which occurred at 1pm yesterday.
Gardai believe that the man was attacked in revenge for a shooting attack on a pal of Griffin's in Swords last October. The target in that incident survived and the man shot yesterday was threatened shortly after the attack because he was on the rival side in the feud.
The victim of the shooting remained in a "critical but stable condition" with gunshot wounds in intensive care today.
The man was sitting in a parked car with a male relative in a layby at Naul Road close to Dublin Airport, where a diner and Christmas tree stall were in operation, when a dark coloured saloon car pulled in. A gunman -- wearing an ice hockey mask -- got out of the car and walked calmly up to the victim's car before opening fire.
The victim was hit twice in the arm and fragments also entered his chest.
The assailant was described as being 5ft 10ins to 5ft 11ins and was wearing a high visibility jacket.
The victim is believed to have been targeted by associates of child rapist Griffin who is serving life for sexually assaulting his partner's daughter.
Griffin, a major crime figure from Sheriff Street in Dublin 1, headed the gang which split following the rape allegations.