The parents of a man who died aged just 22 from a one-punch attack in Melbourne's CBD have made an emotional plea for witnesses to their son's death to come forward.
Shannon McCormack, 22, died after he was punched and fell to the ground, striking his head, outside the Queens Bridge Hotel on May 27, 2007.
He had stepped in to break up an argument between a friend and another man after leaving a Southbank nightclub shortly after 4am.
Mr McCormack died a week later as a result of his injuries.
Police have raised the reward for information from $100,000 to $1 million in a renewed attempt to solve the case.
Mr McCormack's parents Cheryl and Bill McCormack said the pain of their sons death had never gone away.
"Every time we have Christmas … every time there's a family function there's an empty chair … there's always someone missing, and it's very hard to deal with," Bill McCormack said.
They said they hoped the $1 million reward could prompt new information from witnesses.
"Surely they've got a conscience, but all we can do is just plead that someone comes forward."
Detectives on Wednesday also re-released CCTV footage and images of a man they wish to speak to about Mr McCormack's death.
The man is described as being between 165 and 175 centimetres tall with a thin to medium build, and light brown or blonde spiky hair.
Police said he was wearing a light purple or blue T-shirt and light blue jeans on the night of the incident.
Images of two other men who were with him, and may have information about the assault, have also been released.
Detective Inspector Tony Combridge said Mr McCormack's death would be "lodged in the memory" of many Victorians.
"It was one of the first one-punch deaths which sadly became all too common in the years following, and I know his family have campaigned tirelessly for greater awareness around this issue," he said.
Mr McCormack's parents have been involved in raising awareness around the issue of one-punch deaths and violence associated with nightclubs.
Bill McCormack said he never realised the scale of the issue until his son's death.
"You see these random events in the paper every day … and then you realise there's an epidemic of it," he said.
Detective Inspector Combridge said it was highly likely that those involved in the incident had spoken to others about it.
He urged anyone with information to come forward.
"It may be that they were from regional Victoria or interstate and visiting Melbourne or it might be that, given 15 years have passed, these were Melbourne people who have since left the city," he said.
"All we need is a name and we still believe this case can be solved."
Anyone with information can call Crime Stoppers anonymously on 1800 333 000.
