A 60-year-old man died in hospital after being assaulted.
The man was was left fighting for his life after being attacked on Thursday morning in the Cartron Point area of Sligo.
He was taken to Sligo General Hospital where he died on Sunday afternoon.
"The office of the State Pathologist has been advised and the post-mortem is scheduled to take place tomorrow," a Garda spokeswoman said.
A 29-year-old man was arrested in connection with the incident and is being questioned at Manorhamilton Garda Station.
Meanwhile, a 28-year-old man arrested on Friday night has been released from custody. A file is being prepared for the Director of Public Prosecutions.
Detectives have appealed for anyone with information to come forward.