A violent Dublin gang boss is being quizzed by detectives on suspicion of involvement in the feud murder of Kane McCormack.
He was taken from his cell in Mountjoy Prison yesterday morning and arrested by gardai.
The gang boss, who was once a member of the infamous Westies mob, is suspected of having a "significant" role in McCormack's murder, and was one of the last people to be seen with him.
McCormack (24) was shot three times near the Meath/Kildare border.
His body was discovered on December 2, 2017.
In the immediate aftermath of his remains being found, members of the Emergency Response Unit raided his Dublin home as part of the investigation.
Gardai believe McCormack's killing is linked to the Hutch/Kinahan feud, which has claimed up to 19 lives.
His father, Noel 'Duck Egg' Kirwan, was shot dead outside his Ronanstown home in December 2016.
The gang boss arrested yesterday morning is suspected of involvement in other murders and has connections to the Kinahan cartel.
He was arrested in connection with the 2013 gun murder of Lithuanian crime boss Gintaras Zelvys.
He has also survived at least one attempt on his life, carried out by his former associates in the Westies gang.
"Gardai investigating the murder of Kane McCormack have arrested a male in his 40s in relation to the investigation," said a spokesman.
"The male is currently being detained at Ashbourne Garda Station.
"This is the second arrest in relation to this investigation."
While the mob boss arrested yesterday is suspected of a primary role in the murder of McCormack, gardai believe it was a 38-year-old Finglas criminal who was the actual trigger man.
A theory is that McCormack was targeted because in the wake of his father's murder, he was heard frequently making threats of revenge against the Kinahan cartel.
McCormack, also known as Kane Kirwan, had been formally warned by gardai that his life was in danger.
Gardai were acting on information that the Kinahan cartel would strike over fears McCormack could seek revenge for his father's killing.
It later emerged that there was a €40,000 bounty on McCormack's head.
This was offered up when the cartel became aware of his threats.
When he failed to return to his west Dublin home in the early of hours of December 2, there were major concerns about his safety.
This led to a tense situation when a close female associate of McCormack arrived at the chief suspect's house and made inquires about McCormack's whereabouts.
She was instructed by a woman to leave the property.
Investigators have established that McCormack parked his 04D silver Peugeot 307 vehicle in the car park of Aldi in Clonee on the day before his body was found.
CCTV footage shows him getting into a dark saloon car, which drove out of the car park and turned right toward Dunboyne.
The risk of a hit attempt on his life from the Kinahan cartel was considered so great that, on appearing in court in November 2017, his solicitor asked that his next court date not be read out due to the "threat on his life".
He was facing ammunition charges after he was allegedly caught with 50 rounds of .32 ammunition after detectives stopped and searched a car in west Dublin.
McCormack was well known to gardai and had links to the Hutch gang, as well as other dangerous criminals in the city's drugs trade.
Gardai believe McCormack was hiding out in a caravan owned by major crime figure Cornelius Price in the months before his death.
McCormack, originally from Clonee, Co Meath, survived a hit attempt earlier in 2017, after which gardai provided him with security advice.
On that occasion, he was stalked for several days by a Kinahan death squad before gardai staged a dramatic intervention moments before the hit was due to be carried out.
That hit attempt was ordered after the cartel became aware McCormack had been spending a lot of his time at a house in the Ballyfermot area.
Gardai believe that the hitmen were on their way to murder McCormack when they were intercepted by armed officers.