Newshub has been told about possible problems with the vetting of the alleged Christchurch gunman when he was granted a firearms licence.
Joe Green used to manage arms control for the police and still advises them on it. He said there appears to have been "no home interview" during the alleged gunman's vetting process.
"That would start raising concerns in my mind if I was involved in the licensing," he told Newshub.
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Green said the alleged killer may have deliberately sought to get his license in the Waikato district to make it easier for him.
"There've been some concerns expressed around that district - especially around the workload on the arms control staff," he said.
And there were other apparent red flags - in determining whether a person is fit and proper to hold a licence, police usually conduct an interview with their spouse, partner or next of kin.
"The person who knows the applicant best - I'm told that didn't happen in this case," Green said, adding that interviews that were conducted seemed problematic too.
"I understand the two referees that were interviewed were a father and son and that they knew the applicant primarily through an online chatroom," he said.
Newshub put all of Green's concerns to police in an email. They said they wouldn't comment while the investigation's ongoing, and because the matter's before the courts.
Police Commissioner Mike Bush said on Thursday the police will be "working through every one of those suggestions so that when we answer you we can definitively having known all the facts".
It may be another thing for police to address in the wake of terror.