Gardai are satisfied that their murdered colleague Adrian Donohoe was lured into a trap and deliberately ambushed.
Senior officers say the armed robbers, who gunned him down in cold blood, were intent on murdering him as he approached them.
He was blasted in the head with a shotgun from almost point-blank range.
Last night the focus was on a cross-border gang, which is mainly based in south Armagh, as police on both sides worked closely together to track down the killers.
Officers are hopeful a detailed forensic examination of the dark-coloured Passat car, which was used in the getaway, will provide vital clues.
The car was found burnt out yesterday afternoon in a wooded area in south Armagh, not far from the Mountain Lodge Pentecostal Church at Darkley where three worshippers were murdered by the INLA and another seven injured in a massacre in November 1983.
The vehicle was destroyed but gardai and the PSNI believe a technical examination will yield some evidence.
Officers insisted that it was still too early to determine whether the gunmen belonged to a criminal gang or a dissident terrorist group.
Gardai sifted through the available intelligence at a case conference in the investigation headquarters where Det Gda Donohoe and his wife, Caroline, both worked.
Det Gda Donohoe's patrol colleague was held at gunpoint after the murder while the raiders then stole ?4,000.
The killers knew from surveillance that they had carried out on the credit union at Lordship, outside Dundalk, that a garda escort was always provided for officials as they brought their cash on Friday nights after late opening to a