The Garda Ombudsman has launched an inquiry after a recently retired garda detective shot himself fatally in the head at Carrick-on-Shannon garda station after gaining access to the station's armoury.

The 55-year-old garda, originally from Co Donegal, retired from the force three weeks ago. He went to the Carrick-on-Shannon station yesterday at 10.30am and told his former colleagues he needed to finish work on a file.

He was given the code to access the district detective office and from there he went into the station's small armoury room, which contains a locked steel safe containing weapons. He then opened this locked safe and shot himself in the head with an Uzi sub-machine gun. His body was discovered by a garda sergeant.

The retired detective had spent the majority of his career based at Carrick-on-Shannon.

The local community was yesterday in shock at what happened.

"He was one of the soundest men you could ever meet. There was never any sign that he had any problems. Out of the 50 or so current or retired gardaí in Carrick-on-Shannon, he would be the last one anyone would suspect of doing something like this," said a source.

"He was big into GAA and competed in athletics nationally. He was a go-to guy in the guards and was well liked and regarded. He was very active in the local community as well. He was enjoying his retirement, playing golf and taking it easy. It's just very, very sad for his family."

The retired garda is married and is believed to have three grown-up children and one grandchild.

The Garda Síochána Ombudsman Commission (GSOC) probe is likely to question why, despite no longer being a garda, the former officer was permitted to enter private rooms where loaded firearms are stored.

In April 2008, a detective garda attached to the National Bureau of Criminal Investigation was found dead at Harcourt Square in Dublin with a gunshot wound to the head.

Paul Gilton (48) from Swords had been on a night out with colleagues at a nearby bar when he returned to his office and used his official Sig Sauer semi-automatic pistol to commit suicide.

The GSOC investigation caused controversy with allegations that investigators had treated the case with insensitivity and tried to "take over" the probe.

All of the country's detectives are issued with personal firearms which are usually stored in gun lockers at their station or in their own homes, subject to permission.