The suspect in the brutal killing of a brave Irish police officer fired 15 shots at him, hitting him up to five times, after grabbing the gun during a tussle.
Detective Garda Colm Horkan (49) was shot dead by a man after a struggle in which his attacker wrestled his gun from him and then emptied the weapon's magazine.
The gunman fired the full clip of 15 bullets, hitting Garda Horkan multiple times.
Garda Commissioner Drew Harris described Mr Horkan's death as "an attack upon society".
The deadly incident shortly before midnight on Main Street in Castlerea, Co Roscommon lasted just over four minutes.
It is understood Castlerea Garda Station had received a number of calls shortly before 11pm reporting that a local man, known to gardai, was driving a motorbike in an erratic manner up and down the Main Street of the town.
It's understood the motorcyclist was speeding without lights. Following the reports, a number of gardai began to patrol the area in search of the motorcyclist who had by this time gone to ground.
Shortly before midnight Mr Horkan, who was on his own, came upon both the motorcyclist and the suspect in his killing walking together along the main street.
A number of eyewitnesses have reported to gardai they saw the motorcyclist flee the scene.
He is not believed to have been involved in a struggle with Mr Horkan or in his subsequent shooting.
It is believed Mr Horkan approached the other man and the incident quickly turned into a confrontation.
Mr Horkan was said to have been pushed and shoved as he radioed for assistance.
Once a call has been made on these devices, the next 30 seconds is automatically recorded.
It's understood that through this and a number of witness accounts investigating, gardai have a clear picture of events.
During the struggle, the man grabbed his gun and began firing at him until he had emptied the clip.
The incident took less than five minutes. As Garda Horkan slumped to the ground, other officers quickly came to his aid in response to his alert.
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 station.
The suspect 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.
The former PSNI Deputy Chief Constable said Castlerea had lost a "really beloved member" of the community.
He said he was deeply saddened by the death of his colleague and the thoughts of all personnel in the Garda organisation were with the family, friends and colleagues of Colm Horkan and with the members of the detective unit in which he served.
Speaking in Castlerea, Mr Harris added: "I can certainly say at this moment in time that there is no chance at all of a bigger picture in terms of organised crime or a subversive.
"What we have here is a random act and a violent act which has led to the death of Detective Garda Horkan.
"It is tragic and it is an attack upon us all.
"Policing is an extension of good citizenship and we should acknowledge that this demeans and belittles us all.
"It grieves us all as a society that this has happened. It is not how we view ourselves and it is not how we wish to be seen."
Mr Harris said Mr Horkan "served the communities he worked in with distinction and pride".
He added: "Today is a terrible reminder of the significant services, including the ultimate sacrifice, that gardai make to keep people safe."
Last night the suspect was being questioned at Castlerea garda station under section 30 of the Offences Against the State Act and can be held without charge for up to 72 hours.
He was also medically examined by a local doctor while in custody.
After he had graduated from the Garda College in Templemore, Colm Horkan spent the first three and a half years of his career in Finglas in west Dublin.
He served in Castlerea and Ballaghaderreen for the other 21 years until he became the 89th member of the force to be killed in the line of duty.
The murdered garda is a native of Charlestown, Co Mayo.
He lived with his father having been predeceased by his mother and twin sister. He is also survived by his four brothers and a sister. The Garda Ombudsman was notified about the incident but will not be carrying out separate inquiries to the garda investigation as Mr Horkan did not fire the weapon.
Gardai said last night they were trying to establish the full circumstances surrounding the shooting and were trying to trace anybody who had been in Castlerea's Main Street or surrounding streets, particularly at the junction with Patrick Street, between 11.30pm and 12.15 am.
The Garda Representative Association's president, Jim Mulligan, said: "Colm was a gentleman, known for his kindness and commitment to helping other people." He added: "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."
Police closed the centre of Castlerea to traffic as investigations continue in the town of fewer than 2,000 people.
A sombre mood pervaded the town following the murder. A Garda member was visibly emotional as she laid a bouquet of flowers at the edge of the town.
Castlerea publican Ollie Hester said he and others in the town are in a "deep state of shock and sadness".
He added: "He was such a lovely man and so well respected in the community here.
"He was an absolute gentleman.
"No-one in the town can get over what has happened to him."
Gardai are appealing for anyone with information about the incident, and for CCTV footage of the scene.
"We understand an image was shared on social media so we are appealing for that as it could be very useful and important to us in this investigation," Mr Harris said.
The murder of a Garda detective, Colm Horkan, in Co Roscommon has sent shockwaves much further afield across this island. He died after a struggle with an individual who seized his gun and fired 15 shots at the then defenceless officer.