A fourth teen has been charged over the murder of a good Samaritan, as police boost patrols in the area.

Aidan Becker, 22, died at Mernda Railway Station in Melbourne’s northeast on Friday evening after intervening to protect a 14-year-old boy from a group of four alleged teenage attackers.

Mr Becker, a security guard who was off duty at the time, has been hailed a hero by members of the public, including his former footy club Yarrambat Junior Football Club who described him as a “very special young man”.

“Aidan was the kind of teammate every club hopes for – selfless, team first and always willing to put others before himself,” the club posted late on Sunday following news of his death.

Police allege Mr Becker, whom they have not referred to by name, was one of several passers-by who stepped in to protect the 14-year-old.

He tried to walk away with the boy but was subjected to a “savage” attack involving punching, kicking and the use of blades, Homicide Squad inspector Nigel L’Estrange said on Saturday.

Mr Becker suffered life-threatening injuries and was treated by paramedics but died at the scene.

Victorian Premier Jacinta Allan said the Violence Reduction Unit would be deployed to the Mernda area in an effort to provide community support and reassurance.

“My thoughts are with the family of the man who was brutally stabbed in Mernda. Our hearts break for them,” Ms Allan said.

But opposition leader Jess Wilson said Mr Becker’s death was just another example of Victoria’s “crime crisis”.

“It breaks my heart that Victoria is now in a state where people are scared in their homes, scared coming home from work,” Ms Wilson told reporters on Monday.

Four male teens were arrested at the scene and have since been charged with murder and armed robbery.

The eldest, Mike Pikos, 18, appeared before Melbourne Magistrates Court on Sunday morning but was not required to speak, and was remanded in custody to return to court on June 24.

Magistrate Steven Raleigh was told it was the teen’s first time in custody and he would be a vulnerable prisoner due to his age and appearance.

A 16-year-old from Whittlesea and a 17-year-old from Geelong were also charged with murder and armed robbery.

A 17-year-old from the City of Yarra was under police guard in hospital over the weekend and was charged with murder and armed robbery on Monday.

They will appear at a children’s court at a later date.

Four male teens were arrested and have since been charged with murder and armed robbery. (HANDOUT/ABC NEWS)

“This is just a tragic situation where our victim here is just a good Samaritan who was trying to do the right thing,” Det Insp L’Estrange said.

“He’s intervened, tried to protect this 14-year-old schoolboy, hasn’t been aggressive at all, tried to remove him from the scene, and as a result of his interaction, he’s now lost his life.”