A man and a woman arrested in connection with a murder in North Circular road last weekend have been released without charge.
On Tuesday gardai upgraded to a murder inquiry their investigation into the death of a man from a gunshot wound to the head.
Gardai have said a file on the two people released, both in their 30s, will be prepared for the Director of Public Prosecutions and the investigation is ongoing
Partially disabled Gary O'Brien (50s), a father of one from Finglas, Dublin, was found dead in a house on the North Circular Road in the north inner city on Sunday evening.
It was initially suspected the gunshot wound was self-inflicted and when no firearm was found gardai were trying to determine if people in the room where he died had moved it.
However, gardai now believe he was murdered and the firearm disposed of in a bid to conceal evidence and frustrate the investigation.
Gardaí are continuing to appeal to the public for information. Anyone with information is asked to contact the Bridewell Garda station 01-6668200 or the Garda Confidential Line 1800 666 111.
While originally from Finglas, Mr O’Brien had lived on the North Circular Road for seven years.
He had one adult child and several grandchildren. He had been in poor health and had limited mobility to the extent he often used a wheelchair.
The house where the victim was found dead was a large rented property converted into a number of unit.
Mr O’Brien had been living in a basement flat and some witnesses have told gardai they saw a woman coming from the basement in a distressed state, and possibly wearing bloodied clothes, on Sunday evening.
Garda sources said the investigation had been upgraded from a suspicious death inquiry to a murder case because of forensic evidence and arising from interviews by members of the Bridewell detective unit with people who knew the dead man.
The property where he was shot in the forehead is in a state of disrepair and gardai found evidence of drug taking and other substance abuse there.
Another two houses, also on the North Circular Road within 1km of the Phoenix Park gates, had been sealed off and searched as part of the inquiry.
Gardai believe these houses were being used as squats and by drug users. They also believe a number of people had been moving between the two derelict properties and the house where Mr O’Brien lived in the hours leading up to his murder.