A 14-year-old from Melbourne's Hume area was arrested on Friday evening and was charged with murder, police said.
He has been scheduled to appear before a children's court.
Mickleham teenager Darweish Mohamed was found critically wounded outside Craigieburn Community Hospital, in the city's north, about 7.50pm on Wednesday.
A staff member from the clinic rushed to his aid and delivered CPR but he died at the scene.
Police arrested two people in the nearby suburb of Pascoe Vale early on Thursday.
A 16-year-old boy from the Goulburn Valley was charged with murder and remanded in custody to appear in a children's court.
A 20-year-old man from Beveridge was also charged with criminal damage by fire and bailed to appear at Broadmeadows Magistrates Court on December 1.
A burnt-out car found at Oaklands Junction has also been linked to the stabbing.
Later on Friday police said a second murder charge had been laid against a 15-year-old boy from the Craigieburn area.
He will also face a children's court.
A 15-year-old girl from the Fawkner area has been charged with affray and theft of motor vehicle and bailed to appear in a children's court at a later date.
Loved ones of Darweish have asked community members to keep him in their prayers.
Family friend Mohamed Bakhit launched a GoFundMe campaign to raise funds to meet his funeral expenses.
"It is with heavy hearts that we share the passing of our beloved brother, Darweish," the fundraiser page reads.
"No family should ever have to go through a loss like this and our hearts are with his loved ones during this incredibly difficult time."
The campaign had raised more than $54,000 towards a goal of $60,000 by Saturday morning.
It asks those who are unable to donate to keep Darweish and his family in their du'as, an Arabic word for a form of Islamic prayer.
Asked about the Mount Ridley College student's death, Victoria's education department confirmed it would provide support to affected school communities.
"The death of any young person is a tragedy," a spokesperson told AAP.
"The death of the young person in a violent incident on Wednesday will be extremely distressing for the local communities involved."
7°C