Though the teen was not known to members of the cathedral, a representative said everyone involved has been affected.
She said they were not concerned with the damage to the building.
"We're more concerned about the damage to the boy's family," she said.
Nelson College head Gary O'Shea said the loss of his former student was "a principal's worst nightmare".
"It's a very tragic loss," he said. "They're all precious but he was a particularly popular young man pretty much liked by anyone."
Mr O'Shea said he had not yet spoken to O'Neill-Stevens' parents but confirmed they had played an active role in his schooling.
"[Nelson] is a small community. He played hockey and his mum was the physio," he said.
"It's that type of small provincial city... students and members of staff are part of that family."
Nelson College observed a minute's silence this morning in memory of O'Neill-Stevens.
Victoria University Hockey Club captain Matt Wilson said he was saddened to hear of the death of the former club member.