Political leaders in Northern Ireland have paid tribute to a Garda officer shot dead in Co Roscommon.
olm Horkan had served with the Garda for 24 years before he was killed in the town of Castlerea, just before midnight on Wednesday.
A man in his 40s has been arrested and was being held yesterday at Castlerea Garda Station.
First Minister and DUP leader Arlene Foster said: "As someone who is from a policing family and as First Minister of Northern Ireland, I send my deepest sympathy to the family and colleagues of the police officer who was killed."
Sinn Fein leader Mary Lou McDonald called it a "shocking, senseless loss" and passed on her sympathies and prayers to his family, friends and colleagues.
PSNI Chief Constable Simon Byrne said the shocking loss of a Garda colleague was "awful news" and extended his support.
"Thoughts from all @PoliceServiceNI with his family, friends and colleagues at such a difficult time," he tweeted.
A statement from the Police Federation of Northern Ireland, which represents the rank and file officers here, said: "We are thinking particularly of our Garda colleague's family and the dreadful pain that they must be feeling at this massive loss."
Justice Minister and Alliance leader Naomi Long said she was shocked Garda Horkan had lost his life while protecting his community.
"I want to express my sincere sympathy to his family, friends and colleagues as they come to terms with this awful news," she said.
SDLP leader Colum Eastwood commented: "My thoughts today are with the family, friends and colleagues of Detective Garda Colm Horkan as they come to terms with this tragedy.
"Police and Gardai across this island put themselves at great personal risk to serve our communities, to lose dedicated public servants like this is tragic.
"I hope that those responsible are brought to justice quickly."
Ulster Unionist leader Steve Aiken said: "This is terrible news - our thoughts and prayers are with the family and friends of this officer and also to all in the Garda."
Taoiseach Leo Varadkar thanked officers across the country who continued to put themselves on the frontline of crime prevention each day.
"This requires regular acts of bravery and courage each day," he said.
"Sometimes the outcome is tragic and a Garda makes the ultimate sacrifice in the course of their duties.
"Our thoughts today are with all those grieving as a result of this tragic incident."
Fianna Fail leader Michael Martin said he was "shocked and saddened" at the killing.
"Our thoughts and prayers are with his family, his community and all his colleagues who continue to bravely protect us all from harm every day."
Irish President Michael D Higgins said the detective's death has been a shock to everyone.
He added: "As President of Ireland I wish to express my deepest sympathy to the family and friends of the garda, and to all those who have been affected by this tragedy.
"An Garda Siochana play a crucial role in our communities and this loss of life is traumatic for our society as a whole."
President of the Garda Representative Association Jim Mulligan said: "On behalf of the GRA, I extend our deepest sympathy to the family of our colleague fatally shot in the line of duty in Castlerea, Co Roscommon, overnight. Our brave colleague died as result of injuries sustained when he was responding to an incident. He was based in Ballaghaderreen, Co Roscommon, in the Castlerea District," he said.
In 1980, two members of the Garda were shot dead near Castlerea in the village of Loughglynn.
Detective Garda John Morley and Garda Henry Byrne were killed by armed bank robbers.
Roscommon-Galway TD Denis Naughten said the community is in shock following the latest incident.
"We are absolutely devastated, shocked and saddened by what we heard overnight," he told the PA news agency.
"A member of An Garda Siochana who was doing his job protecting the community has lost his life in such very tragic circumstances."