Gardai last night interviewed two men who were in a Dublin apartment when Eddie Flanagan was shot twice in the head with an automatic pistol.
The men agreed to help investigators with their inquiries into the fatal shooting of Mr Flanagan (49), who lived at Primrose Grove in Coolock, as garda technical experts completed their examination of the weapon used in the incident.
A 51-year-old man, who surrendered to gardai on Thursday, was still being questioned at Ballymun station about the incident.
The suspect has already told gardai that the shooting was accidental and had taken place while the group were drinking in the apartment.
Gardai were aware there had been four men in the third-floor apartment when the shots were fired and the two witnesses came forward yesterday as detectives were carrying out inquiries on the northside of the city.
Officers are satisfied that none of the men was connected with crime gangs and that the incident arose during a minor dispute.
Detectives were still trying to trace the history of the handgun, which was found in nearby bushes during a search on Thursday morning.
The suspect can be held without charge for up to seven days.
After the questioning has been completed and statements taken from the witnesses, gardai will brief the Director of Public Prosecutions, who will determine if criminal charges should be brought.
Meanwhile, Mr Flanagan's partner Jacinta Daniels told the Irish Independent last night that the victim's 12-year-old son, Conor, had to be moved out of his home after being harassed by local youths.
She said: "They are saying things to him like 'your dad was killed over a can'. It was too much for him, so we had to move him out".
She added that the family were devastated following the death. It is understood that Conor is staying with relatives.
"He was a very popular man, he had friends all over the place, he was just quiet and unassuming," she said.
She added that the family did not know the man who allegedly killed Mr Flanagan and that gardai had not told them anything about him.
"He didn't have any hobbies or anything, he was a window cleaner and just tried to make a few quid doing odd jobs here and there," she said.
Gardai have completed an examination of the scene of the shooting and have also interviewed neighbours who saw men running from the apartment after the shots were fired.
Meanwhile, officers investigating the murder of Continuity IRA man Liam Kenny at his Clondalkin home last week have drawn up a short list of likely suspects.
They believed Mr Kenny was targeted because he had confronted local drug traffickers earlier this year and this resulted in a number of clashes.