Tully was found guilty in March of being the masked gunman who stormed the Ashburton Winz centre on September 1, 2014 and shot dead receptionist Peggy Noble (67) from point blank range and three times shot case manager Susan Leigh Cleveland (55) as she pleaded for her life.
The 50-year-old was also found guilty of attempting to murder case manager Kim Adams. He was found not guilty of attempting to murder case manager Lindy Curtis, who was shot in the leg and badly injured hiding under a desk.
Today at the High Court in Christchurch, Winz survivors told how they had since been treated for Post Traumatic Stress Disorder (PTSD).
Kim Adams, who felt a "whoosh" past her face from a bullet Tully aimed at her, and colleagues Jane Hayman Walker and Leigh-Ann Hydes, all say they now suffer from PTSD and anxiety, brought on by the horrific scenes they witnessed that day.
Ms Hydes recalls it "as if it was yesterday", and for weeks couldn't sleep, she said in a harrowing victim impact statement she read out today.
The deaths were heartbreaking for the "wonderful tight knit family" where they were more friends than colleagues, Ms Hydes said.
The stress of September 1, 2014 resulted in her undergoing psychiatrist counselling, where she was diagnosed with PTSD.
She described Tully as an "evil man", whose clever "game playing and antics" had manipulated the victims, the justice system, and court for his own means.
Colleague Jane Hayman Walker, who managed to flee the building, said she thought she was going to die that day, and that her children would lose their mother.
Ms Adams is "thankful to be alive".
The shooting still haunts her and has changed her life, she said.
Krystal Bishop said Ms Noble was the matriarch of their small family.
"Peg has always been a rock for us," she said.
She added that "everyone has the right to go to work and return home safely''.
Tully's executions of Ms Noble and Ms Cleveland were "callous, cold blooded and calculated", said Crown prosecutor Andrew McRae, who suggested the starting point for Tully's sentence was a jail term of at least 33 years.
In the 61 seconds he spent inside the building, Tully moved "purposefully, methodically", only targeting Winz staff, despite a number of civilians being in the office that day.
He went to the Winz office that day, specifically wanting to kill as many staff members that he could, Mr McRae said.
That aspect elevated it beyond the case of William Bell who was sentenced to 33 years, reduced to 30 years on appeal, for murdering three people at Mt Wellington-Panmure Returned Services Association in 2001.
Tully was found to be mentally capable of facing charges of double-murder and attempted murder after a hearing under the Criminal Procedure (Mentally Impaired Persons) Act 2003 at the High Court in Christchurch last year.
Mr McRae said that while Tully had showed traits of anti social personality disorder and narcissism, it was not sufficient to classify him as having a disorder.
Amicus James Rapley, who assisted the court during the trial where Tully was not legally represented, believed that the qualifies for a minimum imprisonment period of 17 years or more.
A prison term of 23-25 years was a more appropriate starting point than 33 years, Mr Rapley argued.
While Tully was found fit to stand trial, Mr Rapley said some mental health issues must have been at play, because "no normal person would react in that way".
Tully say quietly for most of the sentencing.
However,, when Mr McRae was outlining the resentment Tully had harboured towards Winz staff, and the strong sense of entitlement he held, Tully interjected, "Objection, your honour."
Justice Cameron Mander told him to be quiet, and that he'd have an opportunity to speak later.
Speaking from the dock, Tully said he wanted to "refrain from saying too much" until appeals were heard.
However, he alleged a "major cover up by the Crown" regarding disclosure and evidence, and further claimed he didn't have access to a lawyer.
Tully sacked at least six defence counsel.
He said he wasn't in the "correct frame of mind at the time" and that he "clearly suffers" from a mental disorder.
"If I was guilty and went out and killed two people, I'd take it, and say, 'That was me'. But obviously that was not the case and I refute the accusation," Tully said.
Tully, who has previous convictions for threatening to kill and presenting a firearm, went there with an intention to kill them, the judge said.
Justice Mander said he had no doubt that if staff hadn't fled the building, or if staff weren't fortunately absent that morning, there would likely have been more fatalities.
They were "cold blooded executions", particularly callous and brutal, he said.
"This type of crime is rare in New Zealand," Justice Mander said.
Justice Mander said Tully was a "very dangerous person" who was very capable of extremely violent actions.
He held a high risk of harm, which meant that there is a need for the community to be protected.
For those reasons, he sentenced Tully to life imprisonment with a minimum non-parole period of 27 years.
Tully will be 77 before he can be considered for parole.