Benjamin Glenn Hoffmann pleaded guilty mid-trial in November to intentionally killing Hassan Baydoun, 33, Michael Sisois, 57, and Rob Courtney, 52, and the manslaughter of 75-year-old Nigel Hellings, on June 4, 2019.
The 48-year-old was sentenced in the Northern Territory Supreme Court on Thursday to three life sentences for the three murders and 15 years for manslaughter, with Justice John Burns refusing to set a parole date.
"I am satisfied that this is case where the court should order that you should be sentenced to life in prison on each of the charges of murder and no non-parole period should be fixed," he said.
"You engaged in a deliberate course of seeking out those who you felt had wronged you with a view to killing them. As it turned out you killed four innocent people.
"These were men who had family and friends. People whose lives have been altered forever by your cowardly, egocentric behaviour ... Your conduct was brazen with you committing these offences openly and in the vicinity of witnesses."
Hoffmann was high on methamphetamine when he shot the four men dead while hunting a man named Alex Deligiannis, who he believed had stolen his ex-girlfriend, Kelly Collins.
He shot Mr Baydoun four times from less than a metre away with a double-barrel shotgun at the Palms Motel in central Darwin.
Mr Hellings was gunned down through the front door of his apartment block about 800m away.
Hoffmann's next victim was his mate, Mr Sisois, who he shot in the head in the car park at the nearby Buff Club bar and restaurant.
Mr Courtney was murdered at an industrial yard at Darwin Recycling, about 2.5km away.
He was found with 69 injuries, including 36 stabbing and slicing wounds, multiple blunt force injuries and a gunshot wound.
After Hoffmann killed Mr Baydoun he moved through the Palms Motel searching for Mr Deligiannis, who had previously lived there.
One of his other victims was Damita Jerome, who Hoffmann shot in the legs after he burst into her room where she had been sleeping with her boyfriend.
Outside court, Ms Jerome said she hadn't recovered from the incident but was "thankful" for the sentence Hoffmann had been given.
"I've been waiting such a long time and it's finally been dealt with. I'm just glad justice has finally been served," she said.
Hoffmann and Ms Collins met in early 2019 in a drug rehab centre, where the pair made plans to move in together after they left the program.
But two weeks before the shootings, Ms Collins sent Hoffmann a text message saying she was in love with Mr Deligiannis and had returned to prostitution.
"Things spiralled out of control with Kelly," he told the court during previous sentencing submissions.
Hoffmann alleged a group of men had been supplying Ms Collins with drugs, raping her and forcing her to work as a prostitute.
He told the court the pair met "naturally" while they were drug-free at the rehab centre after he was released from prison but her regression had left him vulnerable.
"I tried to save her. I feared for my life and my girlfriend," he said.
On the day of the killings Hoffmann said he believed Ms Collins, an ex-prostitute, was in danger and likely to have been physically harmed.
"I had full visions of Kelly being held against her will as a hostage. The night before I was convinced I'd been poisoned and I believed she had been too," he said.
Hoffmann was also sentenced for six other charges, including three counts of recklessly endangering life, drug possession and one of threatening to kill.
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