Hospital security guard Aidan Becker was fatally stabbed at Mernda train station, in Melbourne's northeast, on Friday evening after rushing to the boy's aid.
The 22-year-old escorted the schoolboy away from the group but was allegedly pursued and attacked on his way out from the station.
Despite the efforts of paramedics, Mr Becker died at the scene.
Four male teens were arrested at the scene on Friday evening and have since been charged with murder and armed robbery.
The schoolboy's family paid tribute to Mr Becker in a statement released by Victoria Police on Tuesday, saying they were "deeply saddened by this heartbreaking loss".
"He showed extraordinary courage and compassion in risking his life to save our son," they said.
The family requested privacy as they come to terms with the incident.
"Our family will carry his bravery and kindness in our hearts forever," they said.
"We hold your family in our thoughts and prayers."
It follows an earlier statement from Mr Becker's family, released via his friend Chris Katelaris on Tuesday.
"The Becker family are grieving the unimaginable loss of their son and have asked that their privacy be respected as they come to terms with this devastating tragedy," the statement read.
"The outpouring of support from the public has been deeply appreciated, and the family are grateful for the kindness and compassion shown during this time."
The statement was shared to a GoFundMe page launched by Mr Katelaris to support the family.
On Tuesday afternoon it had raised nearly $70,000 towards a goal of $90,000 from more than 1300 individual donations.
The eldest of the four accused teens, Mike Pikos, 18, appeared before Melbourne Magistrates Court on Sunday and was remanded in custody to return to court on June 24.
A 16-year-old from Whittlesea, a 17-year-old from Geelong and a 17-year-old from the City of Yarra have also been charged with murder and armed robbery.
They will appear at a children's court at a later date.
The incident has sent shock waves across the Mernda community and prompted calls for action on youth violence across the state.
Dozens of bouquets and several handwritten notes have been left near the site of the incident, with local residents hailing Mr Becker a hero.
The incident revived painful memories for Lalor mother Jane Lazz, whose own son died aged 23.
"It was under different circumstances, but I know the pain of it and the consequences for a family," she told AAP in Mernda.
"It changes your life to lose a child," she said, adding her son had played for the same football club as Mr Becker.
Victorian Premier Jacinta Allan said she was scheduled to meet with Mr Becker's family later on Tuesday.
"It's an opportunity for me to sit and listen," she told reporters.
"And also express my deepest, deepest sympathy for someone who was a strong young man, a proud member of the local community who has been killed in the most awful, violent and tragic of circumstances."
Ms Allan confirmed her government's Violence Reduction Unit was on the ground working to understand what led to the incident.
"These acts do shock us all," she said.
"They shouldn't be happening."
Opposition Leader Jess Wilson has claimed the incident was the result of the Allan government's failure to address Victoria's "crime crisis".
Laws came into effect in Victoria on Friday allowing children as young as 14 to be sentenced as adults for more types of violent crimes, including machete attacks and serious armed robberies.
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