Investigators are appealing to anyone who was in the area at around 4.15am to come forward.
The Garda Ombudsman Fiosrú is investigating the circumstances surrounding the death of a man in Dublin city last week.
An incident involving the serious harm of a 51-year-old man on O'Connell Street in the early hours of last Friday the 15th of August was referred to Fiosrú.
The man has since died and a post mortem exam is due to be carried out.
Investigators are appealing to anyone who was in the area at around 4.15am to come forward.

BREAKING: DJ Carey Jailed For Five-And-A-Half Years
Kildare Superintendent Among Officers Promoted As Part Of Senior Garda Operational Reassignments
BREAKING: Man Arrested On Suspicion Of Murder Following Death Of Ryan Weir Gibbons In Kildare Town
"Hope At Last" - Horsepasstown Residents May Soon See End To Six-Year Boil Water Struggle
Kildare Among Worst-Hit Counties As Teacher Shortages Hit Special And Disadvantaged Schools
Focus Ireland Founder Sr Stan Dies Aged 86
Pearse Doherty Claims Government Misled Homeowners On LPT Hikes As Deadline Nears
Minister Announces Nationwide IPAS Security Review Following Drogheda Fire