Another incident she told was when her son felt punished after foregoing normal protocol to save a man's life. Mary said her son was put on supervision for six months, during which, his family say, he felt belittled and bullied by management.

"I could see he was losing confidence in himself," said Mary. "He became distant," said Jeremy Avis' father, Jim.

"It's bullying that erodes people's confidence. It just does. It kills them, it destroys them," Mary told RNZ.

Their son was not alone. The other nurse who killed himself in 2013 left behind a note to his colleagues on the ward where he worked at Tauranga Hospital: "I hope you are all happy now that I'm gone. I look forward to meeting you all again in Hell!"

A number of other staff had since come forward saying they felt bullied, ignored and in some cases had been sacked after speaking out.

Former staff member Ana Shaw, who left Tauranga Hospital four years later she started, said she felt bullied in the workplace.

She said she remembered a staff member tampering with her patient notes.

No matter how many times I raised bullying issues, no matter what I raised, nothing was ever actioned," Shaw said.

The Bay of Plenty DHB chief executive Helen Mason said the suicides were devastating.

"These have been distressing events for all involved; for the families and also for friends and work colleagues," Mason told RNZ.

But she the DHB found "significant and material differences" in the accounts given by the staff. The DHB had denied accusations that the organisation has a bullying problem

"The DHB is firmly committed to an anti-bullying culture and take any allegations of inappropriate behaviour very seriously," Mason said.

RNZ revealed between April 2017 and March 2018, the DHB recorded 13 formal bullying complaints: three were unsubstantiated; three were substantiated; seven are still under investigation.

Bullying was considered a psychosocial health risk in a workplace and, under the Health and Safety at Work Act, employers have a legal obligation to deal with it or they could face prosecution.

RNZ reported that out of the 100 bullying complaints received by WorkSafe between 2013 and 2017, only nine were investigated. None resulted in enforcement action.

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:

 LIFELINE: 0800 543 354 (available 24/7)
 SUICIDE CRISIS HELPLINE: 0508 828 865 (0508 TAUTOKO) (available 24/7)
 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