Homicide Squad detectives are investigating the death of a woman following an incident in Narre Warren South on Monday.
Emergency services were called to a residence in Springvalley Way to reports multiple people had been seriously injured about 1pm.
A 70-year-old woman and a three-year-old girl were transported to hospital with serious injuries.
A 42-year-old woman was flown to hospital but sadly later died.
A 15-year-old male was arrested at the scene and taken to hospital under police guard with serious injuries.
Investigators are yet to determine the exact circumstances but are not looking for anyone else in relation to the incident.