The teenager was approached by a group of eight to 10 men on Tuesday afternoon outside Brimbank Shopping Centre in Deer Park.
Witnesses told Nine News that some members of the group were carrying knives and baseball bats and stabbed the teen “multiple times” in the chest and stomach.
The group ran off, but six were arrested on nearby Billingham Road a short time later. They are yet to be charged.
Foa Galuega, a family friend of the victim, said the teenager was a “good kid”.
“He goes to church. He comes from a good family, a humble family. It’s just so unfortunate this has happened to him,” Ms Galuega said.
She said the fight broke out over an online conflict.
“I think it’s all got to do with social media and bullying and things that they say online and they came after him,” she said.
Another friend of the victim said he tried to intervene in the fight. “We came and pushed them off and then it was too late because he already got stabbed,” the friend said.
Bystanders told Nine they applied pressure to the boy’s wounds before an ambulance arrived.
Paramedics treated the teenager at the scene, but he could not be resuscitated.
Hours later, a fight broke out at the scene involving about 30 people.
Footage of the second brawl posted on social media shows people running into the taped-off crime scene.
A person can be heard in the footage shouting, “I’ll kill you” while bystanders yell “Stop”.
Three men were arrested over the second fight.
A police officer was taken to hospital and another man was treated for a cut to the head.
Homicide detectives are investigating.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or make a confidential report at www.crimestoppersvic.com.au.
Anthony is a sports and general news reporter at The Age.
Rachael Dexter is a breaking news reporter at The Age.