Homicide detectives are investigating after reports of a fight between a group of people at a home at Rye, on Victoria's Mornington Peninsula, shortly after 4am on Monday.
Police believe a man and a woman arrived at the home and became involved in an altercation with the residents.
The 29-year-old man who lived in the home and a woman who was visiting - who is yet to be formally identified - were found inside the property with gunshot wounds.
"It appears that a firearm or firearms have been discharged, and a man who lived that property and the woman that attended that property were seriously injured," Victoria Police Detective Superintendent Janet Stevenson told reporters.
"Emergency services did attend and gave medical assistance, but unfortunately both of them passed away."
Police believe another man who attended the home with the woman left in a car before officers arrived.
A manhunt is underway for the shooter.
Police are still investigating his identity and are unable to provide a description of the car.
"We are very concerned. We don't know if there is a firearm still outstanding, so we're giving a lot of urgency around the apprehension of that male," Det Supt Stevenson said.
"They were known to each other.
"We're not expecting that they're a danger to anyone else in that area."
Homicide detectives and Victoria Police are combing the street for clues. (Diego Fedele/AAP PHOTOS)
The 29-year-old man killed in the shooting is known to police, Det Supt Stevenson said.
Homicide Squad detectives are keen to speak to anyone who may have information, CCTV or dash cam footage in relation to the incident.
"Just contact police if you have any information whatsoever, and that includes if you see someone that you believe might be involved - don't approach," the police superintendent said.
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