A gunman fired 15 shots at a brave garda, hitting him up to five times, after he grabbed the officer's weapon during a violent altercation.
Detective Garda Colm Horkan (49) was murdered on Main Street, Castlerea, Co Roscommon, shortly before midnight on Wednesday in a horrific killing that has shocked the nation.
His weapon was wrestled from him in a struggle, and the gunman emptied the magazine.
He fired the full clip of 15 bullets, hitting Det Gda Horkan multiple times.
The Herald understands that shortly before 11pm a number of calls were made to Castlerea Garda Station reporting that a man was driving a motorbike in an erratic manner up and down the Main Street of the town.
It is understood he was speeding without lights and causing fear to local residents.
Following the reports, a number of gardai began to patrol.
Shortly before midnight Det- Gda Horkan, who was on his own, came upon the motorcyclist and another man walking together along Main Street.
A number of eyewitnesses have reported they then saw the motorcyclist flee the scene before any altercation began. He was not involved in the shocking events that followed.
Witnesses then saw two men involved in a tussle. One of them was Det Gda Horkan who was calling for back-up on his garda radio.
Once a call has been made on these devices, the next 30 seconds is automatically recorded.
It is understood that through this and a number of witness accounts investigating gardai have a clear picture of events, which lasted for just over four minutes.
As Det Gda Horkan slumped to the ground, other officers quickly came to his aid.
An ambulance crew also arrived on the scene but they were too late to save his life.
A suspect, in his 40s, was arrested nearby and taken for questioning to Castlerea Garda Station.
The attacker is understood to have had mental health issues in the past.
Gardai said the incident was not provoked by a personal grudge and appeared to have been motivated by the man's reaction to being questioned.
Garda Commissioner Drew Harris described the murder as a random act, adding: "This is tragic and it is an attack upon us all. Policing is an extension of good citizenship".
Last night the suspect was being questioned under section 30 of the Offences Against the State Act. He can be held without charge for up to 72 hours.
A couple of hundred people gathered on the Main Street in Castlerea last night for a vigil.
A small marquee was set up and tributes were led by local Fianna Fail councillor Paschal Fitzmaurice and parish priest Fr John McManus.
Heavy rain lashed down as the small town mourned the garda's passing.
"The terrible sad occasion that happened here last night is a tragedy that I suppose we will never, ever forget," said Cllr Fitzmaurice.
Supt Goretti Sheridan also paid tribute to her garda "friend and colleague".
"I want to thank everyone for coming this evening, it means a lot to us," she said.
"We're obviously devastated at the death of our friend and colleague Colm. We appreciate your support."
Loughlynn native Mildred Byrne was one of the many locals who attended the vigil.
She recounted the story 40 years ago on July 7, when two gardai, Detective John Morley and Garda Henry Byrne, were shot in Ballaghaderreen, where she was shopping at the time.
She remembered coming up on the scene and saying a prayer into the ear of Gda Byrne.
"All you could see was the car with the windscreen smashed," Ms Byrne said.
"Two guards that I knew very well, used to play badminton with them, Henry Byrne lying on the road, with his head where there was just a bolt fire.
"My first reaction was to go on my knees and to say the Act of Contrition into his ear, and when you think about it afterwards, you'd think we'd be afraid.
"But we weren't, because he was still warm," she recounted tearfully.
Former local councillor and Castlerea resident Danny Burke said Wednesday night's events brought back the harsh memories of the two Castlerea-stationed gardai being shot in 1980.
"I haven't felt as sad since then, I'll be honest with you," he said.
"On July 4, 1980, my mother died suddenly. Detective Garda Morley organised the guard of honour for my mother and she was brought to the cemetery on July 7.
"His colleague Henry Byrne stood at the corner up there and gave a garda salute.
"Two hours later, we were having an after-funeral meal and word filtered through that they were now dead.
"It brought back awful sad memories to me today. I haven't felt as sad since 1980 and I'm going to take a while to get over it.
"These men are out there protecting us and it's a very sad thing that they can't go about their duties.
"This is how they are rewarded."
He also said that he knew Det Gda Horkan personally.
"He was well known, well liked. He always dealt with matters with the most dignified manner," Mr Burke added.
"He was always very approachable and I had a great friendship with him over the years through the football."
l Hero detective shot with his own weapon after tussle
l Attacker believed to have had mental health problems