A source close to the inquiry says the killer is alleged to have picked his targets and even reloaded his firearm before shooting the third victim.
The gunman barged into the office on Monday morning waving a shotgun, his face covered with a balaclava. The source says he walked into the office and looked at a staff member, turned to first victim Peggy Noble and fired at her. She died instantly.
The gunman allegedly then turned and shot a second female staff member and stopped to reload his gun.
Seconds later, it is alleged, he eyed up a customer, then spotted a third Winz staffer and pulled the trigger.
Watch: Shooting suspect rejected help
Staff at an electrical company across the road from Winz unwittingly recorded the alleged killer's movements. Electraserve general manager Blair Watson described the footage, given to police yesterday.
Mr Watson said his impression of the gunman was of someone who was calm and quite controlled.
"He rode up on his bike and sat there for a couple of minutes quite composed before putting his balaclava on and getting his gun ready." Mr Watson said the footage showed the man looked in the building's windows and casually walked inside. In less than a minute he came out and again his movements were unhurried. He put his gun in his backpack, unlocked his bike and cycled off. Mr Watson said the man only moved at pace once he was on his bike when someone was giving chase.
A Winz client said she walked past the alleged killer as she went in to see her housing manager.
She saw what she thought was a long black stick poking out of his backpack, that she later realised was a firearm, and heard someone yelling at him. Not realising what was happening, she walked into the office.
"I thought 'where is everybody?' And then I looked down and saw a person on the floor covered in blood," said the woman, still shaken last night. "It was so horrible. I got in my car and cried all the way home."
Russell John Tully, 48, appeared in the Christchurch District Court yesterday charged with the murder of Peggy Noble and Susan Cleveland, and attempting to murder Lindy Curtis.
He limped into the dock in his bare feet.
No application for bail was made, and he was remanded in custody to reappear later this month. Police later said Tully did not hold a firearms licence.
Social Development Minister Paula Bennett, who laid flowers in memory of Ms Noble and Ms Cleveland at the Ashburton Winz office yesterday, said the pair's colleagues were coping as best they could. "Right now they just want to be together ... Talk it through.
"There's lots of tears."
She also said Tully's case file had been reviewed and she was adamant there was no fault on the part of Work and Income.
A hearse took away at least one of the bodies about 11am yesterday.
Peggy Noble
Peggy Noble was renowned at Ashburton's Work and Income centre for being "hard but fair". But friends say the 67-year-old's uncompromising approach to work was designed to ensure people didn't take advantage of the welfare system, or be rewarded for laziness.
She was a big-hearted person who bent over backwards to help people, they say. Her partner Don, a shearer, is too upset to speak about his loss.
He is being supported at the couple's flat just 250m from Monday's bloody scene by his son and daughter.
Her Tainui whanau are coming down from the North Island to the town where Ms Noble was so well known.
"She was good at her job, hard but fair ... she certainly didn't deserve that ending," said one friend who played competitive euchre with her.
Ms Noble's long-time neighbour Lyn Kamate, 63, yesterday paid tribute to "the most kind-hearted person I know. She was a brilliant friend and neighbour".
The Ashburton Returned and Services Association will hold a minute's silence tomorrow for Ms Noble.
Mrs Noble was a member of the RSA, Radio New Zealand reported, and was well known at the association.
"I remember Peggy coming into the club every Thursday night, as she has done for a number of years," Ashburton RSA president Barbara Costello said.
"Always coming into the club with a smile on her face and always a kind word to say to anyone. Whether she was treated with respect, she treated everyone else with respect.
"She was a fabulous lady."
- Kurt Bayer
Leigh Cleveland
Leigh Cleveland was a quiet-spoken woman who loved her dogs.
The 55-year-old Work and Income worker was one of two people killed in Monday's shooting in Ashburton.
Friends and family said it was Ms Cleveland's love of dogs that defined her.
"She never married or anything like that, so that has sort of been her life," Ms Cleveland's mother Kathleen said.
"Her interests were always animals, she loved them."
Ms Cleveland grew up in Alexandra with two brothers and a sister. As a girl, she was interested in horses and had a pony. In her teens, she worked with draft horses at a farm in Fairlie.
She worked as a civilian for the New Zealand Army Band before moving to Work and Income, where she worked for more than 10 years.
Ms Cleveland initially worked for Winz in Christchurch, but transferred to Ashburton after the quakes. Friend Debbie Renga said she would miss a "wonderful person".
- Nikki Papatsoumas, Susan Sandys
Lindy Curtis
Lindy Curtis dropped her grandchildren off at school and preschool on Monday morning. Shortly after she was being rushed to Christchurch Hospital with a life-threatening wound.
Born and raised in South Africa, the 43-year-old moved her family to New Zealand give them a better life, a safer life.
The mother of two daughters came to New Zealand and enrolled the girls in school in Methven.
She took a job in the international department at Mt Hutt College and quickly made an impression on staff.
One former colleague told the Herald that Ms Curtis was a lovely and very intelligent woman.
Ms Curtis went on to open a coffee shop in Ashburton and in recent years had purchased a house in Rakaia with her new partner, Mark Higginbottom.
She sold the cafe before taking a job at Winz and had recently taken on the care of her eldest daughter Stacey's three children.
- Anna Leask