Five men were inside a home at Canley Heights in southwest Sydney on Tuesday evening when they were approached by two men who opened fire.
Police attended the scene after receiving multiple triple zero calls around the same time a number of the men presented themselves at nearby hospitals.
A 28-year-old and a 32-year-old arrived at Liverpool Hospital about 8.30pm with gunshot wounds.
The younger man died a short time later, while the 32-year-old is in stable condition with a neck wound.
About 10 minutes later, two other men - a 23-year-old and a 22-year-old - presented to Fairfield Hospital both in a serious condition.
The 23-year-old received care for a gunshot wound to the neck and the other was treated for a shoulder injury.
The fifth man, a 19-year-old, arrived at Liverpool Hospital an hour later with superficial injuries to his arm, and remains in a stable condition.
Local police commander Craig Middleton said officers were investigating whether the victim was linked to a Sydney crime gang as they searched for a motive.
"We are aware of some organised crime links, although I can't confirm that at this stage," he told reporters on Wednesday.
He confirmed officers from Taskforce Falcon, which was established almost a year earlier to tackle gangland violence, were involved in the investigation, alongside the homicide squad.
"This is a very brazen violent attack on five people inside their home," Det Supt Middleton said.
"We believe this is a targeted attack although the motive for this attack is unclear at this stage."
Police are still searching for the two shooters, who they believe left the Canley Heights site in an SUV.
Premier Chris Minns emphasised police were acting as quickly and efficiently as possible to arrest the men.
"These are shocking crimes and we don't want to see it on Sydney's streets - it's lawlessness," he said.
"It is distressing to see violent people in our community conduct this kind of assault on other Australians in our community, even if it's from a rival criminal organisation as is often speculated.
"It can never be justified, it cannot be tolerated."
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