A cross border hunt has been launched for the gang who shot dead Detective Adrian Donohoe while he was escorting a cash delivery van to a credit union in the rural village of Lordship on Friday at around 9.30pm.
The gang, who opened fire on the officer without warning, made off with €4,000 during the raid at Cooley Road.
A technical examination on a burnt out Volkswagen Passat is being carried out in connection with the murder.
The vehicle was found in Fews Forest near Keady in Co Armagh on Sunday afternoon, about 25 miles away from the shooting in Co Louth.
The possibility that a Northern Ireland-based gang was involved in the killing of Garda Donohoe has not been ruled out.
The 41-year-old and his wife Caroline were both officers at Dundalk Garda Station. Adrian Donohoe is the first serving police officer to be killed in the Republic in 17 years.
Parish priest Padraig Murphy said that a cloud of darkness has descended upon the local community.
Recalling Friday night's events, the priest said: "It was a harrowing scene - people were totally bewildered and could not believe what had happened.
"This is a rural community, a close knit community in many respects, and a very, very scenic area of county Louth. The last thing we would have expected was something of this nature to happen in our community."
Fr Murphy continued: "This is not something we could have envisaged."
The local priest said the victim was "very much devoted" to his wife, but particularly his children.
"He absolutely adored his two children," he said, before going on to describe him as "a big man, with a big heart."
Fr Murphy said his family have been left "absolutely devastated," finding the fatal shooting "difficult to come to terms with."
At the victim's local GAA club, St Patrick's, the flags fly at half mast as a mark of respect.
A book of condolence has been opened for the man who coached for underage teams at the club.
Alan Duffy, the club's chairman, described him as "a role model for the club's teenage boys."
"Adrian was a big man in stature. He was a gentleman - very, very generous, very, very kind.
"He gave an awful lot to the club.
"It's going to be a huge void."
The First and deputy First Ministers offered their sympathies to his family, friends and colleagues.
"We must all work together on both sides of the border to make sure they are caught for this murderous deed," they said in a joint statement.
Taoiseach Enda Kenny said: "It has left a family without a husband and father and the Garda Siochana without a brave and valued member."
On Monday, gardaí carried out searches around the murder scene. The Flurry River outside Lordship was also searched by specialist police divers for potential clues.
"We have in excess of over one hundred Gardaí involved, included specialist national and regional units," a spokesperson from An Garda Síochána said.
"We are liaising closely with our colleagues in the PSNI and acknowledge their support and assistance.
"An Garda Síochána would like to acknowledge the huge amount of public support we have received since the tragic event," they added.
"This support means a great deal to the family, friends and colleagues of Detective Garda Adrian Donohoe and is a source of great comfort at this difficult time."
A funeral service for Mr Donohoe is expected to be held at St Joseph's Church, Dundalk on Wednesday.