Det Gda Adrian Donohoe may have recognised his killer and that was why the gunman opened fire, gardaí suspect.
Detectives are also investigating the possibility the raiders did not expect there to be an armed Garda escort for the cash delivery at Lordship Credit Union, north Louth, last Friday.
Garda sources said the same gang was thought to have robbed the cash delivery at the same location in 2011, when there was only a uniformed and unarmed Garda escort. At that time they got away with €62,000.
It also emerged yesterday that “staunch republicans” were coming forward offering gardaí help against the gang.
While the Garda investigation is following a number of theories, a particular line of inquiry is being actively pursued.
This is centred on a known criminal who Det Garda Donohoe has had dealings with before in Co Louth and who detectives suspect might be the trigger man. At least three other individuals, including two brothers, have also been identified as possibly being part of the five-person outfit.
The gang, based in the north Louth/south Armagh area, is made up of members from their mid-teens to mid-20s.
Detectives are hoping that one of the five raiders will crack and turn on the triggerman, or that somebody on the edges of the gang will leak information.
Garda sources said the gang is coming under enormous pressure, not only from gardaí, but also from serious criminals and militant republicans in the area.
One source described as “extraordinary” the fact that “staunch republicans” were approaching gardaí saying they would offer any help they could.
Gardaí had initially nominated two brothers from north Dublin, suspected of murdering two innocent men in Finglas last year, as suspects. However, sources said these have been ruled out and that the main suspects were a cross-border gang of young criminals.
Detectives suspect Det Gda Donohoe recognised the killer when he stepped out of the car, even though the gunman had his face covered. Sources said the killer “didn’t give him a chance” and shot him dead and did not allow his colleague, Det Gda Joe Ryan, come to his aid.
Garda sources said there was no point arresting the main suspects until they first gathered all possible information and evidence. They will start on the edges of the gang and move in.
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