GARDA Commissioner Martin Callinan has warned the murderers of Detective Garda Adrian Donohoe: "Keep looking over your shoulder."
He said at a press conference in Dundalk garda station that the investigation team were "tirelessly maintaining their inquiries to ensure his killers are brought to justice".
Today marks the first anniversary of the cold-blooded gunning down of the detective garda at the Lordship Credit Union in Bellurgan, Co Louth.
The garda chief outlined the mammoth investigation that has been undertaken by gardai to date, describing it as "huge and very complex".
He revealed that in the past 12 months the investigation team has taken over 2,100 statements, gathered 400,000 hours of CCTV footage, collected over 1,200 exhibits and carried out more than 30 searches under warrant.
To date, nobody has been charged in relation to the brutal murder of the garda (42) on January 25, 2013. The detective was gunned down in the car park of the credit union while providing an armed escort for the staff, who were carrying cash for lodgment.
Several of the main suspects in the five-man gang fled the country in the aftermath of the shocking murder and the Garda Commissioner confirmed that officers have travelled to several countries to gather intelligence and evidence. He thanked the FBI, the PSNI and the Dutch police for their help.
"We believe we know the identities of the people who carried out this crime," he said, adding: "We are keeping a very close eye on the target."
Responding to a suggestion that some people may be too frightened to give information to the gardai, he urged them: "Come forward and help us, we will make sure no harm comes to you."
The commissioner added that anyone threatening people who wished to help the inquiry would be dealt with "very, very severely".
The commissioner told how Detective Donohoe's bereaved wife Caroline and their two children were uppermost in his mind at this time "as we remember a man who involved himself wholly in his family, his community, and in his job".
Meanwhile, Sinn Fein leader Gerry Adams has denied that his party has any knowledge of the identity of the murderer.
"I do not know who killed Adrian Donohoe," he said. He said that Sinn Fein was doing everything in its power to help bring the killer to justice.
Mr Adams added: "I am very disappointed at the suggestion that I am not using my influence or that Sinn Fein is not using its influence.
"To depict that the people of the border region are protecting or are covering the people who killed Adrian Donohoe is wrong. We have made it clear that this gang should turn themselves in. We think that anyone with any information should bring it forward to the PSNI or the gardai."
A candle-lit vigil in the detective's memory will be held this evening at the spot in Bellurgan where he was murdered.
It will walk to St Pat's GAA Club, which he was so involved with. An anniversary Mass was held yesterday in the Redemptorist Church in Dundalk.