The 15-year-old boy was arrested by police at the scene and taken to hospital, where he remained under police guard with serious injuries on Tuesday.
Chief Police Commissioner Shane Patton said those involved were part of the same family.
“It’s an absolutely tragic incident out there. Homicide are involved, one person is deceased and three family members including that teenager are in hospital under guard. It’s an absolute tragedy,” he told radio station 3AW.
“Obviously homicide are conducting significant inquiries and forensic analysis at the scene. It appears to be involving family members.”
Neighbour Karl Kunze was at home working in his garden when the incident occurred.
He saw a woman crying hysterically on the phone in the front garden.
“I came around the front to get the green garden waste bin and I saw an ambulance out the front blocking [my] driveway, a couple of police cars and the young lady, the mother of the baby, was sitting on the lawn just over there crying on the phone,” he said.
“She was screaming.
“I just asked her if she was alright but then I saw a policeman at the door and I heard one of them say on the radio, ‘one ambulance, you better make it two’,” Mr Kunze said.
He also saw a man yelling in the street. “Some guy came running over and said, ‘my baby’s inside’.”
Mr Kunze said he was shocked that something so horrific had happened in the normally quiet home.
“You hear about all the time, but you know, you don’t expect it next door,” he said. “I was gutted because I didn’t hear any screams or nothing and the radio wasn’t blaring.”
He said the family had lived in the home for a number of years and were friendly.
“I used to see the old lady out here picking weeds from the grass,” he said.
“She seemed pretty nice and the young boy, he used to jump the side fence when he came home from school.”
Mr Kunze said at least three ambulances and eight police cars were at the scene on Monday, and that police remained at the property until about 3am on Tuesday.
A police spokesman said investigators are not looking for anyone else in relation to the incident.
An Ambulance Victoria spokeswoman said one person from the scene was taken to The Alfred hospital in a critical condition, while another was taken to Dandenong Hospital and a child was transported to Royal Children’s Hospital.
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Rachael Dexter is a breaking news reporter at The Age.
Ashleigh McMillan is a breaking news reporter at The Age. Got a story? Email me at [email protected]
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