A 49-year-old man has been released on bail pending further enquiries.
A community has been left in shock after a Co Armagh man died following a late-night altercation.
The victim has been named locally as Nigel Burgess.
The incident happened in the Ballinahone Close area of Armagh city at around 10.20pm on Saturday.
When police officers and emergency services arrived, they found Mr Burgess, who is understood to be aged 60, lying on the ground. He was later pronounced dead at the scene.
The PSNI said a post-mortem examination was due to take place to determine the cause of death.
Police arrested a 49-year-old man, who is believed to be known to the victim, as part of the investigation.
On Monday morning the man was released on bail pending further enquiries.
Newry and Armagh DUP MLA William Irwin said the community was in a "state of shock" following Mr Burgess' death.
"My thoughts and prayers are with the family of Mr Burgess at this time," he said.
"Mr Burgess has lost his life in tragic circumstances.
"I know at this stage a post-mortem will take place and the police are questioning one man.
"The post-mortem will take place to ascertain the cause of death."
Local Ulster Unionist councillor Sam Nicholson added that it was a "truly awful incident within a very close-knit community in Armagh city".
"I have spoken to the police and they are investigating the circumstances of this man's death," he said.
"If anyone has any information that can help the investigation about what happened I would urge them to bring it forward to the police immediately.
"My sympathies go to the family, friends and the local community at this time who are affected by this tragic incident."
Sinn Fein Newry and Armagh MP Mickey Brady also spoke of his shock.
"There is shock in the local community following the death of a man after police received reports of an altercation in the Ballinahone Close area on Saturday night," he said.
"A police investigation is now under way to determine the circumstances."
Sinn Fein MLA Cathal Boylan added: "This is the most awful news for the family of the deceased to receive and they should be uppermost in our thoughts and prayers at this present moment."
Detective Chief Inspector Michelle Shaw appealed for anyone in Ballinahone Close on Saturday night and who witnessed an altercation to contact police on 101 quoting reference number 2554 10/04/20.
Information can also be passed to Crimestoppers by calling 0800 555 111.