A police dog handler and his dog tracked Shortcliffe to the basement of a house on Mahia Rd.
The dog handler sent the dog into the basement and crawled in after it.
"Using the light attached to his Glock pistol, the dog handler saw his dog backing away from a man.
"Believing the man was Mr Shortcliffe, the dog handler commanded his dog to bite."
Shortcliffe then pointed a pistol at the dog handler who "shuffled into a firing position and fired two shots at Mr Shortcliffe," the report revealed.
"Mr Shortcliffe fired one shot in response."
When shots were fired, a second officer crawled under the house and both officers repeatedly called for Shortcliffe to put the gun down. Shortcliffe ignored them and pointed his gun at the second officer.
That officer fired one shot at the offender.
After about 15 minutes, fearing for the safety of their colleagues, officers outside the house smashed a hole in the wall so the dog handler and his dog were able to escape.
The second officer remained in the basement with Shortcliffe for 20 minutes before other officers pulled him out.
Shortcliffe surrendered about an hour later and came out of the house with gunshot wounds to his chest and upper arm.
He also had dog bite injuries on his lower body.
He was given first aid and taken to hospital.
"Once the officers were under the house and confronted by Mr Shortcliffe, in a dark, low-ceilinged basement, their only realistic tactical option was to use their firearms," said IPCA chairman Judge Sir David Carruthers.
"Mr Shortcliffe presented a very real risk of death or serious bodily harm to the officers.
"In the circumstances, both officers were justified in shooting the man."
However, the authority pointed to "omissions" by those in command at the time.
The officers trapped in the basement with the dangerous criminal were not kept updated and the second officer, in particular, was in a "very vulnerable position for a significant period of time", said Judge Carruthers.
"Both officers should have been advised that help was on the way and been given instructions about what to do in the meantime.
"The absence of command resulted in field staff making decisions that could have put themselves and their colleagues at unnecessary risk of harm."
Shortcliffe was charged with two counts of using a firearm against a police officer, possessing methamphetamine for supply and unlawfully possessing a firearm.
He is now serving a sentence of 17 years imprisonment on these and other charges.
Counties Manukau District Commander Inspector Julia Lynch acknowledged that communication could have been better.
"The officers' attempts to locate, track and arrest Shortcliffe in an extremely difficult environment were found to be tactically sound and the decision to deploy a police dog was appropriate in the circumstances," she said.
"Police encounter confronting and dangerous situations and are often forced to make quick decisions in order to protect themselves and our communities."
She said the officers reponded professionally and appropriately.
"No officer comes to work wanting to be put in a position where they have a firearm pointed at them and our staff demonstrated high levels of bravery and professionalism in a very volatile situation."
She said briefings were held afterwards and lessons learned.
