Killer was linked to gang in Donohoe murder

Adrian Crevan Mackin - who turned the gun on himself after shooting the garda and his former girlfriend, Siobhan Phillips - was described as an "out of control and highly volatile wannabe terrorist".

The main thrust of the garda investigation now taking place will be to trace the history of the Glock automatic pistol he used in the horrific shooting.

Crevan Mackin was on bail on charges of IRA membership at the time. He was arrested in January when bomb-making components and two replica pistols were found in his home.

Last night, it emerged that he had been identified as among the associates of the ring leaders of the gang responsible for murdering Garda Donohue in January 2013. The gang - protected by Republicans in South Armagh - ambushed the detective and his partner as they were escorting cash from Lordship Credit Union.

It is understood that Crevan Mackin moved with his partner and children to Omeath after he was threatened by rival gangsters, the Continuity IRA, who also murdered Mackin's terror boss Tommy Crossan in Belfast last year.

"Mackin was typical of the kind of out-of-control young thugs who affiliate themselves to these glorified criminal gangs - a highly volatile wannabe terrorist," said a security source.

"He had been associating with members of the two gangs who murdered Adrian Donohue and Paul Quinn - like him they are all drugged-up and highly reckless.

"He reckoned being involved with these gangs was giving him street cred."

Mackin was also connected to the Republican mob responsible for beating Paul Quinn to death in October, 2007. Paul (21), who was also from South Armagh, was singled out after standing up to a local IRA family with strong links to Sinn Féin. Up to 12 men lured him to a farm shed across the border in Co Monaghan and beat him with iron bars and nail-studded clubs.

Yesterday the Irish Independent revealed that Crevan Mackin was under investigation in relation to domestic abuse by Social Services in the North.

He had also been given a suspended prison sentence for possession of extreme pornography relating to bestiality.