The 24-year-old man who died following an incident in the Currynierin area of Derry has been named by police.
Gerard Quinn died shortly after an alleged assault in the Milldale Crescent area of the Waterside estate.
A post-mortem is due to be carried out on Monday.
Tributes to Derry man Mr Quinn have been posted on social media, with many of those who knew him expressing their shock and sorrow at his death.
Confirming Mr Quinn’s identity, PSNI Detective Chief Inspector Michael Harvey said: “Police received a report that Gerard had been assaulted at approximately 10.25pm.
“He was taken to hospital where sadly he later died.
“A post mortem has been scheduled to take place tomorrow to ascertain the cause of death.
“At this time it is my belief that there was some sort of altercation in the Milldale Crescent area and another man was also assaulted though his injuries are not life threatening.”
“A 16 year old male was arrested shortly after midnight and is currently assisting us with our enquiries at Strand Road Police Station.”
Detective Chief Inspector Harvey continued: “I would like to thank the local community for their support in this investigation.
“We have had an excellent response with a good number of people coming forward providing us with important information which is vital in assisting us with our enquiries.
“Anyone who has any information that they think could help but hasn’t yet contacted us is asked to get in touch with detectives at our Incident Room at Maydown Police Station on 028 7137 9793 or alternatively contact the independent charity Crimestoppers and speak to them anonymously on 0800 555 111.”