The aviation security dog that got loose at Auckland Airport , and who was shot dead, was only 10 months old and in socialisation training.
The Civil Aviation Authority has released the series of events that lead up to Grizz's death on Friday morning.
"Something caused Grizz, a trainee detector dog, to escape from his handler while he was being loaded in to the back of the Avsec Explosive Detector Dog unit wagon at Auckland Airport around 4.30am today."
He managed to get through the security area when a gate opened to let a truck through.
Staff found it difficult to locate him as it was dark, and he did not have a permanent handler so didn't respond as well as a dog who does.
As part of his training before undertaking block courses and assessments including the critical task of identifying explosives, he was on an airport environment socialisation programme, and was six months away from graduating.
"We tried everything, food, toys, other dogs, but nothing would work. The area is too vast and too open to try and use mobile fencing," the CAA said.
"All of Auckland's Avsec off duty dog handlers were called in and there was a massive effort to locate and retrieve him."
About 16 domestic and international flights were delayed after Grizz broke free.
After three hours of trying to catch the canine, airport staff directed police officers to shoot it.
Animal right's group SAFE's ambassador, Hans Kriek, said he was "appalled and bewildered" and that the use of a tranquilliser would have been a simple solution.
"I suppose they didn't have one [a tranquilliser], but that's not an excuse. They said they were chasing the dog for three hours, surely they could've got one from Auckland Zoo.''
There were lessons to be learnt, he added, saying the airport had to get a tranquilliser gun.
"There was a non-lethal solution, they were not prepared. We expect that something is now put in place for future incidents, Mr Kriek said.
But police and Auckland Airport say they had no other choice.
"Unfortunately as a last resort they had to shoot him," an airport spokeswoman said.
Grizz was a 10 month old Bearded Collie/German short haired Pointer cross.
The approximate cost of getting a dog like Grizz to final graduation is around $100,000, once they have completed all of the stages of block and on-the-job training.