Adrian Donohoe was diligent, popular officer: Commissioner Callinan

Garda Commissioner Martin Callinan said: “He was a very popular member of An Garda Síochána, a very efficient member, someone who was revered both by his peers and members of the community where he served."

Det Garda Donohoe’s widow Caroline, two brothers and members of his extended family are also members of the Gardaí.

Detectives are still investigating whether subversive elements such as dissident republicans were involved in the murder or whether a criminal gang was responsible.

Commissioner Callinan said: “There were up to four people involved in the actual raid. How many were involved beyond that will remain to be seen.

"We will put all our energy towards finding out precisely who was behind this robbery. It is too early to speculate whether there was a subversive element to this or whether they are ordinary criminals.”

A book of condolence has been opened at Dundalk garda station where the murdered officer was based.

Former colleagues and members of the public have been attending the station with floral tributes and leaving messages of support for the Donohoe family.

Off duty garda officers stationed in Dublin, representatives from the armed forces and members of the public are among those who have paid tribute in the book of condolence which has been placed beside flowers, a candle and a framed photograph of Det Garda Donohoe inside his former workplace. Some of those leaving messages were visibly distressed and embraced a young female officer at the reception who was guarding the book.

Joe Crawley, 34, who lives a mile from the murder scene, said: “It is just shocking. I am angered, disgusted and saddened at the killing. I have never felt such an intense mixture of feelings. It was totally unnecessary.”

A wide police cordon extending for several miles remains in place around the crime scene at Lordship Credit Union at Bellurgan, Jenkinstown which is about seven miles from the border town of Dundalk.

Specialist uniformed technical officers could be seen scouring the hedgerows and bushes area for clues.

Commissioner Callinan added: “Resources will not be an issue. We have many people working on this investigation with the national units assisting the local Gardai. We have the special detective unit the Bureau for Criminal Investigation and all of the specialist units.”

The senior officer said the some people had to make tough choices.

He said: “It is an inescapable fact that there are people out there who are aware of who these people are and I would appeal to those people to come forward and help us. This is a cry for help for An Garda Síochána and from the wider society.”

It is understood the armed gang of four men were waiting outside to rob the Credit Union which stays open late on Fridays.

Det Garda Donohoe approached the raiders and a number of shots were fired before they fled in a grey Volkswagen Passat. It is understood he was hit in the head without warning and before he had drawn his garda-issue weapon.

Det Garda Donohoe was one of two officers on escort duty when the incident happened and had just alighted his vehicle when he was hit.

He was pronounced dead a short while later. Although traumatised, it is believed his colleague was physically uninjured.

It is unclear whether the getaway car – believed to be a dark coloured vehicle fled north or continued south of the Irish border.

A massive all-Ireland man hunt has been launched.

Mr Donohoe was originally from Co Cavan but was actively involved with the community in Co Louth.

He had two children, a boy and a girl and was a keen GAA fan.

Paul Breen, a member of St Patrick’s GAA club, said: “The whole community is shocked – what else could they be? But, for these people, this is just a way of life.”

Two of his brothers are also in the police and are stationed in nearby Swords and Navan.

President Michael D Higgins was also among those leading the tributes. He described the killing as a dreadful crime and said all Irish people would be truly appalled.

Taoiseach Enda Kenny said the murder was an outrageous and appalling act of cold blooded violence.

He said: “(It) has left a family without a husband and father and the Garda Siochana without a brave and valued member.

“On behalf of the Government and of the people I would like to express my condolences to Adrian’s wife and children and to all his extended family at this unbearably sad time.”

Justice Minister Alan Shatter said no effort will be spared in bringing those responsible for the murder to justice.

“The Irish people rightly have great respect and admiration for members of An Garda Síochána and the work they do in protecting the community.

“They will share my revulsion and horror that a Garda has so tragically lost his life in the course of his duties.

“Our thoughts and prayers are with the family, friends and colleagues of Adrian, who lost his life in carrying out his duty in the best traditions of the brave men and women of An Garda Síochána.”

Sinn Féin councillor Jim Loughran, who knows the Donohoe family, said: “Our whole community is in shock. This garda was admired, trusted and respected by all in the locality. He and his young family are part of the daily life of the area. We want to express our heartfelt sympathy to the garda’s family, friends, colleagues and neighbours at this sad time.

“There is no excuse for the murder that took place in our community. Those responsible are dangerous criminals who have no decency. They went out to commit a crime and fully prepared to murder anyone who stood in their way. Serious crime is leaving communities across the country in fear every day.”

The Lordship Credit Union, where the killing took place, was described as a hub of the small community.

It is believed staff were locking up when the incident happened.

Councillor Declan Breathnach said it was not unusual for it to remain open late into the evening.

“It would be fairly busy on a Friday evening, with some people just getting their week’s pay or wanting to sort out money for the weekend,” Mr Breathnach said.

“This was just such a despicable, heinous act. I still can’t believe it but I utterly condemn it.”

Mr Donohoe is the first garda officer to be killed in 17 years.

Detective garda Gerry McCabe was also on escort duty when he was shot dead outside a post office in Co Limerick in 1996. His widow Anne said: “I have to sympathise with the family and the shock they are going through.”

A post mortem examination is due to be carried out at Our Lady of Lourdes Hospital in Drogheda.