Gardaí in Dublin have begun a murder inquiry after a 27-year-old Lucan man, who was assaulted in the city centre last weekend, died from his injuries in hospital on Thursday evening.
They believe Alan Barbour, who worked as an electrician, may have been attacked after he threw a soft drink at a friend.
Mr Barbour was hit once in the head at about 3.15am last Sunday by a male assailant opposite the GPO on O'Connell Street, as he returned home from a night out.
He collapsed to the ground and was taken to Beaumont Hospital where he died five days later.
Gardaí believe there was no prior altercation between him and his attacker, but are investigating the possibility that he may have thrown a soft drink at his friend, perhaps as a "prank".
Following this, he was approached by his killer who hit him once. It remains unclear whether the soft drink hit a third person, prompting the attack.
A postmortem was being carried out yesterday, and was expected to show that he died from head injuries sustained as a result of the attack.
However, gardaí are awaiting the results of further tests to establish whether he died due to the blow to the head or from the injuries received when he fell.
Officers at Store Street Garda station are appealing for witnesses, and are anxious to talk to six people who were seen in the area at the time of the incident.
These include two young girls with whom Mr Barbour and his friend had a conversation prior to the assault, and a group of four men who were passing by at the time. The girls may have been from the northside of Dublin.
Mr Barbour's assailant, who was in the company of two other men, is described as being six feet (183cm) in height, of strong build with a "skin-tight" hair style.
He was wearing dark jeans with a horizontally striped T-shirt. There is a possibility that he may be of Eastern European origin.
Gardaí yesterday released new CCTV images of people who were in the vicinity at the time of the attack.
Det Insp Christopher Mangan, of Store Street Garda station, who is heading up the investigation, said: "We are appealing for anybody who was in the vicinity to come in and talk to us.
"They might not have perceived it to have been as serious an assault as it was," Insp Mangan added.