The chief suspect for the country's latest gun killing shot dead his 22-year-old victim because of a dispute over just €100, it can be revealed.
The petty cash row led to a confrontation between the duo in which the suspect - a 42-year-old drug dealer - was beaten up, badly damaging his "ego and street credibility", sources explained.
Last night, Kildare gardai were continuing to question the man who is suspected of being 'off his head' on drugs when he cycled a BMX up to Jason Doogue and shot him three times in the chest with a 9mm handgun on Friday evening in Athy, Co Kildare.
Mr Doogue was sitting on a wall with up to four friends when the assailant, wearing a balaclava, approached.
The gunman opened fire at close range with a handgun, initially hitting Mr Doogue once.
The victim collapsed over the wall and the gunman, in front of horrified onlookers, then discharged a further two shots at his target.
It has also emerged that the murder suspect, who has connections to a dangerous Ballyfermot-based gang, threatened one of Mr Doogue's pals with the gun just after he shot the young man before he cycled away from the scene.
Sources have revealed that the bungling suspect then made a botched attempt to clean himself in the sink of a female associate's house and that this sink has since been seized by Gardai and removed from the house.
The Herald has learned that the drug dealer, whose mob is linked to a number of pipe bomb attacks and shootings in the Athy area, targeted Mr Doogue because of a confrontation between the two men some weeks ago.
"There was a row over a small amount of drugs, maybe just €100 worth, and the suspect did his usual thing and was acting the hard man," the source said.
"An altercation took place. What happened was that he slapped Mr Doogue in the face - but the younger man was having none of this and he beat the crap out of him.
"The suspect swore revenge because his ego was completely put out of shape and it is suspected he carried out this murder when he was completely off his head on drugs.
"Gardai knew within minutes of the shooting who the chief suspect was, and he was arrested at his home almost within an hour or so."
The handgun used in the murder has not yet been recovered despite numerous searches taking place this week.
Apart from the chief suspect, a teenage male and a woman in her 30s were still being questioned about the fatal shooting last night.
The woman is understood to be well known to the suspect.
Another teenage male who was arrested on Saturday was released without charge on Monday night.
Tensions remain extremely high in the Athy area this week, with sources saying that gardai are monitoring threats being made against associates of the chief suspect in the case by some associates of the murder victim.
It is understood that the investigation is "complex" and officers have been reviewing CCTV and analysing witness statements as part of the probe.
Speaking to the Herald at the scene of last Friday's fatal shooting, a 22-year-old friend of the victim, fighting back her tears, said: "Jason was just waiting to go into his friend's house and have a shower before going on a date with his girlfriend.
"It's terrible what happened him. He had a hard life."
Last Friday's savage murder is just the latest tragedy that the Doogue family have encountered.
In 1995, Jason Doogue's mother, Mary (30), was kicked to death by her ex-lover Stephen Davis (20) in a jealous rage following a night out - and he was later convicted of her murder and served a life sentence.
The jury heard Ms Doogue and Mr Davis had been seeing each other for just over two years at the time of her death.
Ms Doogue was unmarried and had six children. Davis was the father of her youngest child, Stephanie, who was seven months old at the time of her mother's death.