Victorian homicide squad detectives are questioning one of the two men captured on CCTV moments before a fatal assault on a Melbourne street.

Police say they have found one of the men, who is assisting them with their inquiries, but they say he is not under arrest.

Detectives are still searching for the second man who was also seen on security footage just before a 21-year-old Parkville man was kicked in the head by two attackers outside a McDonald’s outlet on St Kilda Road, Melbourne.

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He died in hospital an hour later from his injuries.

Police say the incident was unprovoked and have released CCTV footage which shows clearly two men they allege were involved in the assault about 1.10am on Saturday.

The suspects then fled.

Homicide squad Detective Sergeant Sol Solomon urged anyone who knew the men or had information on the incident to come forward.

Detectives have not released the victim’s name.

Police say he was standing outside the McDonald’s when a fight allegedly started involving the two men, who were also aged in their early to mid-20s and had just bought some food.

“He was grabbed by the arm and violently thrown to the ground head-first, and then kicked to the head,” Det Serg Solomon told reporters.

“He lapsed into unconsciousness immediately.”

Both men were involved in the assault and fled south along St Kilda Road, Det Serg Solomon said.

The victim was taken by ambulance to the Alfred Hospital with critical injuries.

“It’s yet another violent, senseless assault occurring on a public street in Melbourne late at night,” Det Serg Solomon said.

Police say the victim was well dressed in a black suit and shirt but not carrying any identification.

There was no indication he knew his attackers.

“There appears to have been a discussion leading up to the assault. We’re not aware what words were exchanged,” Det Serg Solomon said.

The men are described as Caucasian and of average build and height. The man in the purple, hooded Mossimo jacket, dark coloured pants and a white t-shirt is assisting police.

They are still searching for the man who wore a grey, hooded Mossimo jumper, dark pants and dark shoes.