The man, in his 40s, had come to the attention of Gardai.
The Garda Ombudsman has been notified after the death of a man in Offaly who had come to the attention of officers.
Members of the force were called to a disturbance on Patrick Street in Tullamore at around 4pm yesterday afternoon.
A man in his late 40s was treated at the scene and taken to Tullamore Hospital where he was later pronounced dead.
A post-mortem will now be carried out, with the results to determine the course of the investigation.

Woman Arrested In Connection With Murder Of 6-Year-Old Kyran Durnin
Two New TDs Enter The Fray After Bye-Elections In Galway West And Dublin Central
Rural Housing Supply Below Demand, Report Finds
€1.5 Million Cannabis Seized In Joint Dublin Operation
Calls For Prison Security Review After Inmate Died In Their Cell
Fuel Oil Prices At Highest Recorded Value In Five Years
Over 200 Fines For E-Scooter Offences Issued In Kildare Carlow Area
Planned 72-Hour Ambulance Strike Called Off