Gardaí in Co Mayo are questioning a man in his 20s in connection with the fatal stabbing of Francis Heneghan in Kiltimagh in the early hours of yesterday morning.
The 24-year-old father-of-two was found injured in a laneway off the town's Main Street following a brawl involving a number of people.
He died at the scene a short time later.
A man in his 20s was arrested yesterday evening following an appeal for those involved in the incident to come forward.
He is being held at Swinford Garda Station for questioning.
Gardaí have described the stabbing of Mr Heneghan as a "mindless, senseless act of violence".
Detectives on the murder case believe several people were involved in the savage killing.
The dad-of-two, from Ballyheane, just outside Castlebar, was from a well-known and highly respected family.
His bloodied body was found by gardaí about an hour after another man had been assaulted.
The incident, which shocked locals, happened just four days after a garda was stabbed in the stomach while on duty in the county.
Garda Daryl Mullen remains in a serious but stable condition in Mayo General Hospital in Castlebar, where he underwent emergency surgery.
A 16-year-old youth was charged over the attack on Monday.