A young security guard who tried to stop a robbery on his way home from work was allegedly stabbed to death in Melbourne’s outer north-east.

Emergency services rushed to Mernda Station on Bridge Inn Road just before 6pm yesterday following reports of a group brawl.

Victoria Police detective acting inspector Nigel L’Estrange said the 22-year-old from Mernda tried to intervene in a brawl and protect a 14-year-old schoolboy.

Emergency services combed the scene at Mernda Station.© 9News

“He hasn’t been aggressive at all and tried to remove him from the scene and as a result of his interaction he has now lost his life,” L’Estrange told 9News.

The 22-year-old was found at the scene with life-threatening injuries. He was treated by paramedics but died at the scene.

Police later arrested four teenagers including a 16-year-old, 18-year-old and two 17-year olds.

On Saturday night homicide detectives charged a 17-year-old boy from the Greater Geelong and a 16-year-old boy from the Whittlesea area with murder and armed robbery. They’re both due to appear at a children’s court at a later date.

An 18-year-old man from Mill Park has also been charged with murder and armed robbery and will face the Melbourne Magistrates’ Court tomorrow.

The 17-year-old, who is from the City of Yarra, remains under police guard at hospital and is yet to be interviewed.

Police later charged three teenagers with murder and armed robbery© 9News

Earlier in the day, the 22-year-old’s emotional loved ones consoled each other at the station.

Police said weapons and a machete sheath were found near the scene, where homicide detective spent hours combing for clues.

The exact circumstances surrounding the incident are being investigated.

There will be an increased police presence at Mernda Station in the coming days to reassure the community.

The station was taped off by police following the security guard’s death.© 9News

The incident comes more than a week after the state introduced its ‘adult time for violent crime’ laws.

Under the new rules, Victorian teens as young as 14 who commit crimes such as aggravated home invasions and carjacking will face adult sentences in adult jail.

Government minister Mary-Anne Thomas said the message to young people across Victoria was clear.

“If you commit violent crime you will be serving adult time,” Thomas said.

A 22-year-old man was found at the scene with life-threatening injuries.© Nine

Opposition leader Jess Wilson argued “cops are down and crime is up” under Premier Jacinta Allan.

“In the last 24 hours we have seen the tragic consequences once again,” Wilson said.

“It’s cowardly, it’s shocking and it’s not something we want to see in our streets.”

Anyone who witnessed the incident or with footage is urged to contact Crime Stoppers on 1800 333 000 or report at www.crimestoppersvic.com.au