The experienced officer, who wished to remain anonymous, felt like he had to speak out after the assault.
He had never seen a situation anywhere near as bad as it was at the prison at Milburn, resulting from the "the calibre of prisoner we’re getting".
While his contract prohibited him from speaking to the media, he was worried about his friends and colleagues.
Corrections Association of New Zealand vice-president Paul Dennehy said staffing struggles and an increase in hardened offenders had contributed to a sustained increase in the number of assaults on corrections officers both at the prison and nationwide.
He had been told that in the latest incident one corrections officer was unlocking a cell with two inmates inside, one of whom immediately started punching the officer in the head.
A second officer with him also received several blows to his head.
A radio callout for help was made and while the two officers were waiting for assistance, the second prisoner came out of the cell and started "laying into" the two officers.
Three of the responding officers were injured before the prisoners were able to be restrained and moved to the site’s management unit.
All five injured officers were taken to hospital.
The incident happened in unit 35, where the highest security prisoners were held.
Milburn was taking a lot of prisoners from Christchurch and increasingly becoming the high-security facility of the South.
While the overall prison muster was down, the prisoners who were in custody were those who were at a high risk of violence and threats against staff.
"It’s not the white-collar fraudsters of years gone by," Mr Dennehy said.
Corrections was facing a nationwide staffing shortage and the assault would add to the pressure Milburn staff already faced as part of their daily grind.
While the staffing situation at Milburn was better than most prisons, it faced a shortfall of about 70 staff members across various roles.
"We need more corrections staff ... we’re barely getting by."
Staff were not paid enough for the brutality they faced, resulting in some staff taking a pay cut to go to careers that did not involve assaults, threats to their families or having bodily fluids thrown at them.
In an assault several months ago, a staff member had sustained multiple fractures to the face.
The Government needed to take a firmer stance on prisoners that attacked staff and make the career more attractive, including better pay, Mr Dennehy said.
In a written statement, Otago Corrections Facility director Dave Miller said the two prisoners had been placed on "directed segregation" and police would be notified of the assault.
The assault happened when the prisoners were being returned to their cells and nearby staff responded immediately.
One staff member returned to work yesterday and the others were expected to return next week. They were being supported by managers and the facility’s welfare team.
The prisoners would be charged with misconduct and police would determine if any criminal charges would be laid.
"The reality is the threat of violence is something we cannot eliminate entirely, but we are constantly working to ensure our prisons provide the safest environment possible for staff and prisoners."
All prison sites, including Milburn, had a site safety plan to address violence.
A corrections spokesman said there had been 16 assaults on staff at Milburn this year, none classified as serious.
For security reasons Corrections could not discuss staff numbers in units.
However, unit 35 had been appropriately staffed for the number of prisoners it had on Thursday.
Staff numbers in units could fluctuate, depending on the number of prisoners housed at any time.
The unit was being supported by staff from the site response team, the spokesman said.
— Additional reporting Wyatt Ryder
