UPDATE 3.30pm: ACT Police say a Braddon man in his 20s has handed himself into police and is assisting police with enquiries into the incident.
"Police would like to thank the community and media for their assistance in swiftly providing information regarding the identity of the two men involved in the disturbance with the victim, pictured in CCTV," a police statement read.
EARLIER: It's a familiar scene. It's late at night, after a big evening on the town. Out on the street, groups mill around -- perhaps having just left a club or pub, perhaps planning their next move, perhaps waiting for a taxi home. An argument breaks out, heated words are exchanged... then suddenly, everything changes.
A punch is thrown with no warning, with no time to defend. A head snaps back, a brain shudders in its skull, a young man falls to the pavement -- hard. He lies motionless as onlookers stare curiously, not sure what just happened.
Just days after Queensland teenager Cole Miller died following an alleged one-punch attack, ACT police have released footage of a New Year's Day "coward punch" assault outside a Canberra convenience store that put a young man into hospital for emergency surgery.
Around 2.45am on January 1, CCTV captured two men appearing to be in a heated discussion outside a convenience store on East Row, in the Canberra suburb of Civic. A crowd of other people mill around; several pubs and clubs are in the nearby area.
As the men argued, a third man -- standing behind and to the right of the victim -- clenched his fists and appeared to prepare for a fight.
Suddenly, the third man throws a punch and connects with the back of the victim's head. The victim immediately falls to the ground, his head slamming hard into the concrete footpath. He lies motionless, as his attacker walks away. Another young man walks over to check on the victim, but a crowd of other onlookers simply watch and take no action to help.
"The male victim sustained injuries that required him to undergo emergency surgery," police said in a statement on Friday.
Police have asked the public for information to identify the offender. He was described as being between 170 and 180cm tall, with dark complexion, wearing a grey T-shirt and black pants.
Police are urging anyone who may have witnessed the incident or who can identify the offender to contact Crime Stoppers on 1800 333 000, or via https://act.crimestoppers.com.au.