The Herald understands it is the first time such a serious complaint has been made for a junior grade rugby game.
Ms Gundmundsson said the location of the hearing would not be revealed, and it was not known how long it would take.
It would be over overseen by an independent disciplinary committee made up of about half a dozen people from different professions including the law fraternity.
Its decision would be released through the rugby union.
Parents, spectators and officials were horrified by the incident at the Papatoetoe Sports Grounds that occurred 10 minutes into the second half.
One parent, who did not wish to be identified, said that the player was walking towards the goal posts when he turned around and "gave the ref the finger", before running at him.
"The ref had his back turned and was blindsided by the boy who dropped him to the ground," the witness told TVNZ.
"There was a bit of a scuffle on the ground and then the player punched the referee."
Auckland Rugby Referees Association referee manager Smudge McNeilage said the referee was not physically injured in the attack, but was "certainly affected".
"He was been resting at home, he has certainly been affected by the event."
It was understood the hearing would involve the referee association, the player and his parents, as well as witnesses from both teams.