Police have officially named the 62 year old male who was murdered at a premises in Magherafelt as Brian Coulter.
Major Investigation Team detectives have also issued a photograph of Mr Coulter, along with a specific appeal for information.
It is understood a male relative of Mr Coulter called at his flat on Monday afternoon and disturbed a male in the flat, who fled the scene and was later arrested.
Detective Chief Inspector Raymond Phelan said: “Just after 12.30 on Monday afternoon, (October 18 2021) police received a report that the body of a deceased male had been found at a residential property in the Sandy Braes area.
“Police attended and arrested a man nearby on suspicion of murder who remains in custody.
“I am asking for help from the public to identify sightings and movements of Brian since last Monday, 11th October.
“I am particularly keen to hear from anyone who saw Brian, together with descriptions of anyone who was in his company through to Monday 18th October.”
“If you have any information which you think could help, please contact detectives on 101 quoting reference 944 of 18/10/21.
"A report can be made using the online reporting form via www.psni.police.uk/makeareport . Information can also be provided to Crimestoppers anonymously on 0800 555 111 or online at www.crimestoppers-uk.org."
Mr Coulter had been a serving police officer in south Armagh during the 1980s.
One one occasion he switched a shift with a colleague who was subsequently blown up in an attack.
After the incident, the officer developed an alcohol addiction.
Mid Ulster MLA Keith Buchanan offered his condolences to the victim's family.
"My thoughts are with the family and neighbours who are now mourning the loss of a loved one or neighbour," he said.
"It’s my understanding that a person has been arrested and the PSNI are appealing for information and requesting that anyone who seen or heard anything to contact them.”
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