Ben Hoffmann, 45, allegedly went on an hour-long shooting spree across the city on Tuesday night - killing four men and injuring a woman.
Australian police also say it's possible the Kiwi's actions prevented more deaths.
Police later arrested the suspected gunman, but have provided no other details.
"The guy that actually carried her up was pretty frantic at the time, saying he had opened the door and there was a gunman there with a shotgun and he proceeded to fire upon anybody inside the building". He moved to the inner Darwin suburb of Stuart Park, where further shots were fired, then moved to the adjacent suburb of Woolner.
Buff Club manager John Smellin said club members would consider holding a tribute to the victims, including Mr Sisois, understood to be a well-known figure in the Greek community, who was killed in the club's carpark. As part of his parole he was wearing an electronic ankle bracelet.
"As chief minister, on behalf of Territorians, our thoughts are with the families and friends of the victims and everybody else who has been impacted", Northern Territory Chief Minister Michael Ginner said after shooting.
"This is not the Darwin we know", Gunner said.
Hoffman, 45, was taken into custody on Tuesday night after a shooting left one person injured and four people dead.
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Mr Kershaw said Supt Morgan did a "magnificent job in negotiating with him and subsequently alerting police to his location".
A 23-year-old woman at the Palm Hotel was shot in the legs and remains in hospital in a stable condition.
Mr Sisois told Sky News and the NT News alleged shooter Ben Hoffmann was known to be risky and should have been behind bars.
Police cordon off Palms Motel in Darwin after the shooting.
Australian Prime Minister Scott Morrison, who is now in London for D-Day commemorations, said the shooting was "criminal and violent act".
"We're still trying to establish the intent and the motivation behind this".
There are eight active crime scenes, as police work to piece together what led to the "horrific crime".