This morning, the national secretary for the Public Service Association Richard Wagstaff told NewstalkZB that WorkSafe's decision could lead to changes in workplaces.
"I'm sure that this action by WorkSafe will have made a lot of people stand up and take notice right across the state sector and private sector."
He said it would be about finding a balance between keeping people safe in their workplace without creating a "fortress".
Mr Wagstaff said the shooting at WINZ was "extreme", but workplaces needed to be prepared to deal with threatening and violent people.
"It's not uncommon for people to threaten, for people to get violent, to spit and abuse," he said.
The charge was laid in the Wellington District Court following the conclusion of an investigation that WorkSafe - formerly Occupational Safety and Health (Osh) - began soon after the tragedy.
Front-counter workers Peggy Noble, 67, and Leigh Cleveland, 55, died in the shootings on September 1 last year.
Russell John Tully, 48, has been charged with murdering the pair.
He is also accused of attempting to murder two other staff members - Lindy Curtis, 43, who was shot in the leg and badly injured, and Kim Elizabeth Adams.
Tully also faces other charges, including theft and unlawful possession of firearms and ammunition, and is due back in court in two weeks.
Leigh Cleveland's mother, Kathleen Cleveland, told the Herald yesterday that she was disappointed by WorkSafe's planned prosecution, as it would drag up feelings she had been struggling with.
"You sort of feel you're getting over it and then it brings it up again. But they probably have their reasons [for going to court]," she said.
"It's a bit hard to take it all in, especially after what we've been through."
The surviving victim, Lindy Curtis, did not want to comment yesterday.
While prosecutions against government departments are unusual, they are not unheard of.
Legal expert Graeme Edgeler said the ability to prosecute crown agencies came about after the Cave Creek disaster in 1995, in which a Department of Conservation platform collapsed and 14 people died.
Mr Edgeler said WorkSafe was allowed to prosecute other employers, so it was only fair government departments could face the courts as well.
Reparation paid to victims or families varies across health and safety cases. A WorkSafe spokesman said there was no upper limit for payments.
How the case unfolded
September 1, 2014:
Work and Income staff members Peggy Noble and Leigh Cleveland die in a mid-morning shooting at their Ashburton office. A third person, Lindy Curtis, is injured.
September 2:
Homeless man Russell John Tully is charged with murder and attempted murder.
September 23:
New charges, including unlawful firearm possession, are laid against Tully.
September 26:
It is revealed the Ministry of Social Development hired 200 more security guards to protect staff around the country after the Ashburton shooting.
February 10, 2015:
An independent review recommends better security and training at Work and Income offices.
Yesterday:
WorkSafe NZ files a charge against the Ministry of Social Development of failing to take all practicable measures to ensure the safety of its employees.
