Michael Galvin was off-duty and preparing to ring in the new year at home with his wife Collette when he got a call from his colleagues in Ballyshannon Garda Station.
It was 11.30pm on one of the busiest nights of the year and they were down a sergeant, who had fallen ill.
"Because of the night that was in it, Mick didn't want to let his colleagues down and he immediately volunteered to fill in - that was the type of him, always willing to help his friends and work colleagues," a close friend recalled yesterday.
The sergeant, who had 22 years' unblemished service, put on his uniform and was on duty in Ballyshannon in less than 30 minutes.
Around 12.15am, a call came in that there had been a hit-and- run accident on the other side of the town in which a pedestrian had been seriously injured.
As Michael Galvin and a colleague went to investigate the incident, the garda recognised Sheena Stewart on the pavement on the town's Main Street.
Earlier that night, he and colleagues had given her a lift from Bundoran to Ballyshannon.
Ms Stewart had been distressed and wanted to get a bus home. Sgt Galvin got out to speak to her as she was on her own and still upset. She had missed the bus.
He sought to reassure her and said he would arrange a lift home for her to Letterkenny as soon as he was finished dealing with the incident. He wanted to make sure she got there safely.
It has now emerged that Ms Stewart was sitting in the street when she was fatally injured by a passing taxi 30 minutes after the gardaí left - it was reported earlier this week that the accident took place within a few minutes.
The incident was subsequently referred for investigation to the Garda Ombudsman by a senior officer because gardaí had been the last people to interact with Ms Stewart.
Sources close to the Association of Garda Sergeants and Inspectors have claimed that there was no necessity to refer the case in the first place.
In their initial inquiry, GSOC viewed CCTV footage and compared the statements of three gardaí.
The sergeant's colleagues have told the Irish Independent that he first realised he was the subject of a criminal investigation when he took a call from the Ombudsman in March.
By the time he put down the phone, Michael Galvin's world had begun to unravel, launching him into a spiral of despair which culminated in his death nine weeks later.
Sgt Galvin was told that an investigation had uncovered an "anomaly" between his original statement and what CCTV footage had shown.
The discrepancy that arose related to whether Ms Stewart had been on the pavement or in the road when the gardaí left to answer the emergency call. Sgt Galvin told GSOC that she was on the pavement.
He repeated the content of the conversation to members of his family and at least four colleagues - who have separately spoken to the Irish Independent.
Michael Galvin said that during the call, the suggestion of an "anomaly" quickly became an accusation that he had given a "false and misleading statement" and had "perverted the course of justice".
"Mick was shattered by that call and he told us that he was effectively being blamed for that poor woman's death - he was left with the impression that Sheena Stewart would still be alive if he had done his job properly," a close friend said.
"This was a man who had 22 years' service and was one of the most honest, decent human beings that you could meet.
"But the enormity of what he was accused of overwhelmed and consumed him. All he could see in front of him after that was a prison sentence, the loss of his job and the ability to provide for his family," the friend added.
On May 20, Sgt Galvin and his solicitor met by arrangement with GSOC officials in Dublin, where he was interviewed under caution. He gave the investigators a pre-prepared statement which was read over to him and then signed.
When it was over, the sergeant was more convinced than ever that he would be charged with a crime that he was completely innocent of.
Colleagues grew increasingly concerned that the pressure of the investigation was pushing him into a deep depression.
On Wednesday week last, Sgt Galvin reported for duty and colleagues say that he appeared less troubled than before.
It was a quiet night in Ballyshannon and he watched a programme on TV with a female colleague. Around 1am, he went to his office and began writing a heartfelt, four-page letter to his wife Collette and his three children.
He then went towards the back of the station and took a pistol from a gun locker in a detective office. His colleague heard a faint noise and it was some time later that the officer's body was found.
The astonishing revelation in the Irish Independent - that Sgt Galvin had been exonerated a number of days before his death - has thrown the spotlight back on how GSOC operates.
The fact that he had been exonerated of any wrongdoing several days before by GSOC, and had not been informed, will now be the focus of a judicial inquiry.
The watchdog has given different accounts of when this happened - variously claiming it was five days, two days and one day.
Gardaí have described as crass and insensitive GSOC's decision to open an investigation into another colleague of Sgt Galvin just days after his death. The probe also relates to the death of Ms Stewart.
One senior garda said: "GSOC seems completely indifferent to the fact that this garda is trying to deal with the death of his colleague and friend."