The man, 22, was released from garda custody last night and a garda spokesman said a file will now be prepared for the DPP.
Joe O’Callaghan, a 66-year-old father of three, was found with fatal injuries by his African-born wife, Angie, at their home on Galway’s Lane in Douglas, when she returned home after night-shift work at around 8am on Monday.
It is understood he had suffered severe head injuries. He was pronounced dead at the scene.
The death was initially treated as suspicious but the garda investigation was upgraded to a murder probe yesterday after assistant State pathologist Margot Bolster concluded an autopsy on Mr O’Callaghan’s remains at Cork University Hospital.
While the autopsy concluded that his injuries were consistent with a violent death, a garda spokesman said the investigation team, under Supt Charlie Barry, would not be releasing the results of the autopsy “for operational reasons”.
A man, arrested for questioning in connection with Mr O’Callaghan’s death after he presented himself at Togher Garda Station on Monday afternoon, stayed in garda custody over the last 24 hours.
However, following consultation with the DPP, a decision was made to release him without charge around 9pm last night.
Mr O’Callaghan’s front door was damaged on Sunday night or early on Monday morning after a verbal row on his doorstep.
Neighbours in the cul-de-sac reported hearing a man twice shouting “open the fucking door” before hearing the sound of a door being kicked or being slammed.
However, they such shouting was not unusual at the victim’s home, where late-night parties had been the subject of complaints from neighbours before.
Mr O’Callaghan was originally from the Grange area of Cork and had recently become a grandfather.
His sister, Sheila Thornhill, said she saw him last Saturday morning.
She said he had struggled with various health issues over the years but that he appeared to be in great form at the weekend.
“I hadn’t seen him as good in a long time,” she said.
The manner and circumstances of his violent death had left the family shocked and devastated, she said.
Local councillor Joe Harris, who went to school with Mr O’Callaghan and who met him regularly for coffee, said he had never mentioned any security concerns to him during their meetings.
He said he deserved justice and he urged anyone with information to contact gardaí.
While some forensic examinations were conducted on the house yesterday, it was no longer classed as a crime scene by last night.