"I'm certainly getting attacked, that's for sure, but it's not new to me. A lot of people want to keep things in the dark.
"[The board] hasn't ensured these allegations are being looked at...and I'm not prepared to sit on my hands anymore, to be quite frank."
Two of Dr O'Sullivan's seven children board at the school and he is an old boy who has been on the school's board for eight months.
Conversations he had with children at the school recently showed there were "things happening on the ground" affecting the youngsters, he said.
He did not want to discuss the bullying allegations because some of the cases might go to court, Dr O'Sullivan said.
"I just don't believe that at the moment I can put my hand on my heart and say these kids are going to get the support they need...I'm not just a Johnny-come-lately that's rocking the boat. I have been concerned for a good part of those months [on the board], there needs to be strong governance.
"This school is coming up 100 years and it's put out some amazing leaders. I believe it has that opportunity to be that great school of glory again."
The Herald reported in April about issues at the school, including the roll falling below 100, dilapidated buildings, bullying, infighting and a lack of confidence from its owner, the Catholic Church.
Two recent bullying incidents - including one where a child was attacked with a stick - had involved police, and fears over safety had led to the resignation of a board member, and parents removing children.
The May incident, where a staff member allegedly broke into the boy's room and verbally abused him, was reported to management but nothing was done until he got a letter from the boy two weeks ago, he said.
The Bishop of Auckland showed a lack of faith in the school when questioned, saying he wanted to review the Maori boarding model. There are also fears the church wants to sell off the valuable school land.
Dr O'Sullivan said he was aware there was a lot of work to be done, but his primary concern was safety.
If he was confirmed as chairman of the whanau trust board, which looks after the hostel, at a special meeting this weekend his first move would be to investigate how the alleged assault was managed. He would also look at earlier complaints.
The special meeting was called after it was discovered the board did not have a quorum at the time Dr O'Sullivan was elected chairman.
The Herald understands the boy at the centre of the most recent claims had complained to police and school management.
"I talk a lot about vulnerable kids in my work as a doctor, and I don't want to be a board member who talks a lot about vulnerable kids and doesn't do anything to help. That's why I'm taking such drastic action," Dr O'Sullivan said.
Hato Petera, whose former pupils include All Black Walter Little and the late artist Ralph Hotere, is the sole remaining Maori boarding school in Auckland and one of only six in the country.
Two other such schools, St Stephen's and Queen Victoria, were closed in the early 2000s.
Neither school management nor the recently ousted hostel board chair, Tame Te Rangi, wanted to comment on the board issues or the alleged threat. Previously, the school has responded to questions about bullying by saying it was working to overcome issues and had a positive behaviour programme in place.
Board of trustees chairman Mate Webb said: "The incident you refer to has been managed and documented accordingly, I can assure you of that."
But hostel board member Anthony Kemp said he agreed the board needed a new direction and he would support Dr O'Sullivan as chairman.
Former principal Sir Toby Curtis, who occasionally advised both the school and hostel boards, said there needed to be some proper strategy at the school.
He said Hato Petera was "lucky" to have someone of Dr O'Sullivan's calibre willing to take on the role.
"I am hoping some of his other colleagues who are capable and high achievers may like to come and sit alongside him," Sir Toby said.
The meeting will be held at Hato Petera marae at 11am on Sunday.
Dr O'Sullivan was named Kiwibank New Zealander of the Year last year and Maori of the Year in 2013.
- With additional reporting by NZME. News Service
