A man was shot dead by his friend in a remote townland in Co Mayo after being mistaken for an intruder, gardai believe.
Brendan Kilduff (67), from Sallyhernaun, near Knock, had just visited his pal, a farmer in his 80s, in the neighbouring townland of Coogue.
It is believed that a moment of tragic confusion after Mr Kilduff left just before midnight on Tuesday resulted in his death.
It is understood that after visiting the elderly farmer, Mr Kilduff was unable to start his car. He was then fatally shot as he returned to the farmer's house.
Sources say "all the indications" are that Mr Kilduff, who was single, was "shot accidentally".
Mr Kilduff and the alleged gunman had known each other for many years, according to local sources. Mr Kilduff was a frequent visitor to the farmer's house.
Gardai have been working on the theory that the farmer discharged a number of warning shots after he became suspicious of noises outside his home.
Local sources say the farmer, who has been arrested, was "very paranoid" about becoming the victim of a burglary and may have been concerned that he was about to be targeted by a gang when he discharged shots from his legally-held firearm.
"Both men are very well- respected local bachelors who operate small farms. It is a terrible tragedy," a local source said last night.
Gardai have also been investigating whether the farmer had been suffering from a serious illness recently which may have been a factor in Tuesday's tragic events.
A senior source confirmed last night that the farmer made a 999 call after the shooting.
"He said that he had fired shots after becoming suspicious of noises outside his home," the source said.
"This case is being to referred to the DPP."
Gardai rushed to the scene and the man was arrested. Sources said that while officers are satisfied with his version of events, the case is still being treated as a homicide.
The elderly farmer was last night released without charge and a file will be prepared for the DPP. Mr Kilduff's body remained at the scene overnight on Tuesday.
The car he is believed to have driven to the house was covered in plastic by gardai and shattered glass from its windows could be seen on the ground beside it.
Members of the garda Technical Bureau arrived at the remote scene shortly after 12.30pm yesterday and began their forensic analysis.
Mr Kilduff's body was then brought from the scene to Mayo University Hospital, where a post-mortem was due to be carried out yesterday.
Later in the day, Mr Kilduff's car was transported from the scene for further analysis.
Bloodstains were visible under the driver's door, indicating that he had been shot in or close to the car.
Friends who knew both men said people living in the area were shocked, saddened and stunned at the news as it broke yesterday morning.
Aiden Kneafsey is a neighbour of the man who was arrested, and said he had known him for 59 years.
"He was a farmer living alone. Everyone around here is in shock and they're trying to take it all in," he said.
"It's a very sad day for the village and everybody involved."
Mr Kneafsey said the alleged gunman is a quiet sheep farmer who would have done agricultural contracting in his earlier years, adding: "He's very helpful in the area. Everyone is devastated."
Neighbouring farmers told how there had been a number of burglaries recently and many people, especially those living on their own, were living in fear.
Mr Kneafsey said those targeted by thieves had had items stolen.