The garda shot dead in Roscommon last night had only just become a detective.
Det Garda Colm Horkan was based in Ballaghaderreen and joined the unit at the start of the Covid-19 crisis.
The detective had initially been called out to attend what has been described locally as a domestic incident.
The officer, who has not been named, had stopped a man in Castlerea's Main Street around midnight and after a struggle, his weapon was taken off him.
He is believed to have been shot four times.
A man has since been arrested and is in custody.
Roscommon County Council Cathaoirleach Paschal Fitzmaurice said: “Castlerea is just in shock at what has happened.
“This sort of thing just does not happen around here.
“I am told the garda involved, who was not based in Castlerea, had stopped another man, an incident happened and his gun was taken off him.
“I am told he was shot four times.
"It is such a terrible thing to happen.
"I understand he had only just been made a detective earlier this year, around the time the Covid crisis started."
He added: “This sort of thing just does not happen in Castlerea, let alone Roscommon.
“The last time it did was more than 40 years ago.”
He was referring to the murder of two officers at Shannon's Cross, Aghaderry, Loughglinn on July 7, 1980, about half an hour from Castlerea.
Then detectives John Morely and garda Henry Byrne were gunned down by men alleged to be in the Irish National Liberation Army (INLA).
They had just stolen IR£35,000 from the Bank of Ireland in Ballaghaderreen and Detective Morley and Garda Byrne were in a patrol car that intercepted them as they escaped.
The two officers died in the ensuing gunfight.
Of the detective’s death early this morning, AGSI General Secretary Antoinette Cunningham said: "We are all very devastated.
“It is absolutely devastating news.
“There is somebody in custody, so we have to be very careful of what we say.
"But a Garda has lost his life in an incident on duty and that is all we can think about this morning.
"Our thoughts go to his family and friends and colleagues in Roscommon at this time.
“I spoke to the chief superintendent up there this morning and they are all absolutely devastated at his loss.
"It's very, very tough."
A garda statement issued just after 6am read: “It is with the deepest sadness An Garda Síochána confirms the death of our colleague, resulting from fatal gunshot wounds received during an incident in Castlerea shortly before midnight on Wednesday 17th June 2020.
Minister for Justice and Equality, Charlie Flanagan said: "I am deeply shocked and saddened at the shooting of a Garda member in Roscommon last night and a full murder investigation is underway.
“The brave Detective Garda who died last night died in the line of duty, serving and protecting the community.
"His death will cause untold heartbreak to his family, loved ones and all his colleagues in An Garda Síochána across the whole country.
"It is also a loss to wider Irish society.
He added: "The women and men of An Garda Síochána serve the whole community and work to keep Ireland safe.
"In their everyday duty, they put the welfare of others ahead of themselves, as they work to shield us from harm and to connect our communities.
"It is to them that we turn in times of crisis, including during the current pandemic.
"All throughout this period, Gardaí have been selflessly working to protect our health and wellbeing, in the best tradition of the service.
“As Minister for Justice and Equality, I convey my heartfelt sympathy and condolences to his parents, family and friends and indeed to the whole family of An Garda Síochána.
“Ar dheis Dé go raibh a anam.“
- Updated at 10.45am