"He reacted brilliantly."
Police said the boy pointed the imitation firearm at his victim and shot him three times about the head and face.
The male teacher in the classroom intervened and the offender turned and fired at him, before firing the pistol several more times into the wall.
Mr Aitken arrived after the teacher, understood to be the school's Year 12 dean, detained the boy as he ordered the other students to leave the classroom. The pair waited in the classroom with the boy until police arrived not long after.
"Our emergency protocols kicked into place and the student was detained in the classroom so there were no further safety issues within the school."
Mr Aitken said that despite reports of the victim being shot, there were "no injuries" and the victim's father took him home shortly after.
He confirmed that the two boys knew each other and had had some kind of argument.
"They were known to each other and clearly there was a grievance there from the past but exactly what it was is uncertain at this stage," Mr Aitken said.
"It was completely out of left-field for me. It wasn't something that I would have pegged to the student," he said.
"He had been suspended and was to meet before the board later this week and was obviously unhappy about something."
Mr Aitken said the school had an assembly and parents of students in the classroom had been contacted.
He said victim support would offer its services to affected students throughout the week.
Eastern Waikato Area Commander Inspector Dana McDonald said the investigation was still in its formative stages but police were full of praise of the teacher who intervened.
"The actions of the teacher were highly commendable in that he put himself in harm's way to protect students in the class," said Mr McDonald.
"In most situations like this we ask that people don't put themselves at risk and instead contact authorities by ringing 111 but in this case it appears the appropriate course of action was taken."
The boy was yesterday being assessed at Thames Hospital.
Mr McDonald said police would work with the school and Ministry of Education to establish the course of events and the best way of supporting all the people who were at the school at the time.
The 14-year-old boy will appear in the Hamilton Youth Court today on a number of charges including firearms offences.
- additional reporting APNZ