"Jay" believes jealousy played a big part in turning him into a bully.
When he was growing up in Northland, Jay (not his real name) lived mostly with his grandmother because his parents were not capable of looking after him.
"They were only 17 when they had me," he says.
His aunt and uncle lived nearby, but it was not the same when they turned up to see their son play rugby in Jay's team.
"They are not your parents, I never lived with them," he says.
"You know there's a whole life out there that, for whatever reason, I'm not part of. You want it but you can't get it, so you try to hurt them."
It wasn't just that his parents were absent. Even worse was the way they treated him when, periodically through his childhood, they took him back to live with them in Auckland for months at a time.
Although both worked, their money went on booze and gambling and there was often no food in the cupboard. Jay was left to look after his younger brother and sister, and his mother blamed him when anything went wrong.
"I really felt that she hated me," he says.
"She was more violent than my father was when it came to physical abuse, quite nasty. Verbally as well, the verbal stuff was very nasty.
"I struggled through my school years. That was a big thing for my mother to keep referring back to how dumb and how thick we were.
"I found out really recently that she had been raped by her brother for many years, so I got a lot of understanding of why she was the type of person she was."
His father taught him to be tough.
"I can remember getting into a fight and I can remember my father just beating the crap out of me and telling me you need to go back and sort it out. I think I was only 6 years old."
His father also beat him to make him do his homework.
"He had worked hard all his life and he didn't want that for any of us, which is quite strange for a person that beat the crap out of you. If you look at his own family, it's like looking in a mirror."
For about 10 years from the age of 4, Jay was raped by a friend of his parents who lived with the family.
When he was 8, he was blamed when his cousin drowned while they were swimming together.
Today, he describes his bullying as "suicidal". He taunted much bigger boys to draw them into fights, and he rarely lost.
"I had very few friends really at school," he says. "One friend I still have, we've talked about it. He was my friend but he probably didn't really want to be.
A lot of our friendship was based on fear. For them, it was like, stick with the bully and not be bullied."
When he left school, he got into fights with the Mongrel Mob, but eventually joined it.
"I was looking for a family," he says.
He never thought in those days that he would have a wife or children himself.
"I didn't ever expect to be alive that long. I amazed myself to get to 21, I amazed myself to get to 31. The only reason I got to those stages was because I was in jail."
Today, at 49, Jay goes into schools for Violence Free Waitakere's programme "Violence-Free Begins With Me" to help children avoid the path he followed.
"My message to the kids is that if something is going on, they need to ask for help," he says.
"If you think someone needs help at home, you need to be able to express that to an auntie or get on with some adult. You need to get that message out so that other people can help."
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By Simon Collins Email Simon