A teenager has died after being bashed at a Halloween party that turned ugly on Friday night.

- North Balwyn fight
- Boy, 16, dies after bashing
- Failed to wake yesterday

It is believed Justin Galligan, 16, was at a party in North Balwyn when gatecrashers arrived.

A fight involving up to 15 people broke out in a car park behind the house and Galligan, who was an invited guest, was knocked unconscious.

After he came to, friends took the Kew High School student to his Fairfield home, where he went to sleep, but when his parents tried to wake him in the morning he did not respond.

The year 10 student was rushed to Royal Melbourne Hospital, where he was diagnosed as having a serious brain injury. He was in a critical condition in the intensive care unit and died at 4.30pm yesterday.

Homicide squad Detective Sergeant Graham Guy said yesterday that about 50 people were at the party, and asked for anybody police had not already spoken with to contact them.

"Obviously the people who were involved in the fight, I'd be appealing to them to come forward, with their parents, and let's sort out what happened," Detective Sergeant Guy said.

"At this stage we're still trying to piece together exactly who was involved in the altercation. It appears that the people in the car park may well have been gatecrashers, but it's too early to determine that at this stage."

Detective Sergeant Guy said the assault was an example of the huge ramifications a punch can have.

"It's very disappointing. In my role I've been involved in a few assaults that have had poor outcomes, but I'm at a loss to explain why teenage boys of this calibre would want to get involved in things like this," he said.

Justin's distraught sister, Siobhan, told Sky News her brother "always made people happy" and that his MySpace page had been inundated with condolences.

His aunt, Kathy Neagle-Haupt, described the death as "an absolute tragedy".

"Justin was a beautiful boy who has lived his short 16 years to the full," she said.

A man at the house where the party was held yesterday said it was a "tragic incident" and he was "deeply distressed" about what had happened.