The man was one of three staff members assaulted by inmates on February 11, 2017, resulting in concussion, vertigo and injuries to his left shoulder and arm.
He spent the following six months off work, experiencing dizziness, headaches, anxiety and low moods, and undergoing counselling, according to the psychology adviser, writing in an ACC referral document after his death.
While a psychological assessment demonstrated he had depression and "ongoing cognitive problems," he was allowed to return to work about six months after the assault.
Despite their separation, the ex-partner and the man remained close friends.
Their young daughter continues to struggle with his death, she said.
Before his death, the man told his ex-partner the prison was becoming "scarier and scarier".
But he had been a Corrections officer for much of his working life, and did not know what else he would do.
"He was petrified to go back into that place, not that he would tell you that.
"They sent him back into the same wing, and surprise, surprise, he [dies in a suspected suicide] five days later."
The psychology adviser found the man felt guilty about the length of time it was taking him to recover, while people close to him and a Corrections welfare officer grew increasingly alarmed about his mental health, despite his reassurances.
In the psychology adviser's view, he likely qualified for a diagnosis of a Major Depressive Disorder, and if so, his suspected suicide was probably a result of that disorder.
The ex-partner called on Corrections to provide more support for people returning to work after suffering trauma.
She wrote via her lawyer to Corrections Minister Kelvin Davis last year, enclosing a series of questions about her ex-partner's return to work.
He wrote back, saying he had raised her concerns with officials and told them to look into the matter.
A subsequent letter from her lawyer to the Coronial Services Unit said Corrections was not prepared to engage, but asked for the ex-partner's concerns to be put before the coroner and considered during the investigation.
Corrections regional commissioner Ben Clark said the department would not comment on the specifics of the case while it was before a coroner.
Corrections had "invested significantly" in measures to protect staff from assault in recent years, including de-escalation training, stab resistant body armour and the use of pepper spray.
A wide range of support was available for staff who were assaulted, he said.
The ODT recently reported the concerns of a man who works inside OCF who believed it would be only a matter of time before someone was seriously injured or killed at the prison.
But in the ex-partner's view, that had already happened.
"Corrections are failing in their obligations to provide a safe work environment and there has already been a death as far as our daughter and I are concerned."
WHERE TO GET HELP:
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.
OR IF YOU NEED TO TALK TO SOMEONE ELSE:
• 0800 543 354 (0800 LIFELINE) or free text 4357 (HELP) (available 24/7)
• https://www.lifeline.org.nz/services/suicide-crisis-helpline
• YOUTHLINE: 0800 376 633
• NEED TO TALK? Free call or text 1737 (available 24/7)
• KIDSLINE: 0800 543 754 (available 24/7)
• WHATSUP: 0800 942 8787 (1pm to 11pm)
• DEPRESSION HELPLINE: 0800 111 757 or TEXT 4202