It comes as police work to infiltrate organised crime groups that are targeting “vulnerable” young gang members, getting them to do their “dirty work”, the senior officer said.
“All these things are interconnected,” Mr Hansen said.
On Monday 20-year-old Springvale man Thomas “Tommy” Tran died following an armed brawl in Oakleigh’s Eaton Mall after telling his family he was going to the gym.
It was the fourth fatal knife attack on Melbourne streets in the past fortnight, although the incidents are not related.
Mr Hansen said the impact on families often lasted a lifetime, with police now dispatching extra resources through targeted operations in “hotspots” to track, trace and arrest violent young offenders.
“The impacts of these decisions that are made in the heat of the moment, they will live with your family and your community for years and years to come,” he said. “Be a positive representative of your family, your cultural heritage, your school, your football club and of you.
“The message that I have for these kids is if they could hear these families speak, and see the grief and the pain that they are holding on to, many years after the incident, [they would see] the loss and the hole that it has left in their lives.”
On Tuesday Mr Tran’s distraught family visited Oakleigh’s Eaton Mall to say a prayer after the 20-year-old was killed about 8pm the previous night.
They said Mr Tran had told his family he was going to the gym before they received a heartbreaking phone call.
Mr Tran’s girlfriend Trish Nguyen made an emotional plea for teenagers and young men to stop fighting.
She said her boyfriend of more than two years was a “dreamer” who aspired to be a bodybuilder and wanted to create his own line of gym-wear.
“I just want the real story. I just want to know the truth,” she said.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000.
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Erin covers crime for The Age. Most recently she was a police reporter at the Geelong Advertiser.