"It really, it destroys you. It absolutely destroys you," he said.
"I remember going to the doctor and I just broke down. I felt about an inch tall, I really did.
"I had to go, otherwise I think I would have, well, I would have, I would have topped myself, I really would."
On Monday, when RNZ broke the story of widespread bullying in the police, 21 sworn police officers or non-sworn staff members who had personally experienced or witnessed bullying in their jobs had spoken to RNZ.
They were from different parts of the organisation, based in different locations, and were not at all familiar with one another.
In response to that story, 40 people had come forward, who wanted to blow the whistle on what they said was a toxic culture within the police force.
The former British constable said his direct boss sought to ostracise him.
"Well, he wanted me to be isolated, and it's a difficult job to do in the first place but when you know you haven't really got the back-up behind you, he was putting my life in danger, I thought.
"There wasn't one sort of thing, that was why it took me so long to realise what was happening, if you know what I mean.
"It was just one small thing after another, after another, after another."
They said the complaints were often directed straight to their bully - who was more often than not their direct supervisor.
Mr Bush was asked what he would say to the 40 people who had come forward anonymously.
"I say to them, anything that gives you concern, come to see us, we'll deal with it, because it's not the way we lead inside the organisation.
"We have a very positive, very healthy culture inside the organisation, and I'm here to ensure that's maintained and everyone that works for us is safe."
Police minister Stuart Nash told RNZ in a statement the bullying issue was an operational matter for the Commissioner to handle.
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.
