"The shooting was justified and police considered or used other tactical options before resorting to a firearm.
"The immediate actions of several officers in response to the threat posed by Mr Hussein demonstrated clear thinking and professionalism in a rapidly unfolding critical incident."
Hussein broke into Redwood Primary School at about 7am on March 15 and threatened caretaker Noel Batstone and a teacher with a knife.
He then hijacked a food truck driven by Ms Robin and forced her to drive across Christchurch at knifepoint.
During the drive he stabbed her in the shoulder.
She was able to escape while Hussein was momentarily distracted by a traffic jam and appealed for help from a city council worker.
While the 55-year-old man was calling police, Hussein got into his car and held a knife to his throat.
The worker was stabbed six times after deliberately crashing his car into a wall in an attempt to escape.
Two police officers used pepper spray and a taser in a confrontation with Hussein at Hoon Hay Rd.
Hussein then ran at a third officer, who shot him in the shoulder and wrist from a distance of about two metres with a Glock pistol.
Sir David Carruthers said he had looked at whether the officer should have armed himself, the number of shots fired and whether other tactical options had been attempted before deciding the shooting was lawful.
He said police arranged for medical care to be given to Hussein as soon as he was shot.
Hussein was sentenced to six years and six months in jail for possession of a knife, kidnapping, and intent to cause grievous bodily harm on September 20.
