Former police negotiator and detective Lance Burdett spoke to Newstalk ZB's Mike Hosking this morning about the siege and how police were handling it.
The alleged gunman has now been arrested and the siege is over.
He said police procedure for this type of incident is trained around the world - it's called Cordon, Contain and Appeal (CCA).
"There will be attempts made to contact him through all sorts of mediums, whether it's through loudhailer to get him to talk on the phone - that's the ultimate, to get him talking on the phone. Use of social media - if that's available, they'll be doing that. Any way of getting him to communicate."
Mr Burdett, who is now a negotiator instructor, said things could "turn on a knife edge" during situations like this.
"People are so unpredictable, particularly when they're emotional. So it's a bit like 50 per cent of murderers in prison are from domestic related incidents - ordinary people just suddenly snap and change."
He said he did not know the specifics of this case but said it is very difficult when offenders are emotional - their reactions are so unpredictable.
"We can generalise about things, however it's not always the case."
He said the negotiation process was about judging a person's behaviour.
"I've heard that there is some social media out there. Someone will be watching that if they can and just having a look and assessing that. Hopefully they'll be talking at some point, if not already, and then it's a well-known technique of just establishing a rapport through building empathy."
Mr Burdett said the offender's rational thought would have gone by this stage.
"So the right side of our brain is where all his thinking will be - the defence side. Which is the unclear side, the emotional side. Logic's on the left side of your brain and that disappeared a long time ago.
"Talking to somebody rationally - you can't do. What you can do is follow a step by step process."
He said it was the right decision to keep family out at the moment. "That can be a resort later."
"I ran the negotiations in Napier [and] we did that at one occasion and it didn't end well. Some say it did. We like to get everybody out safely and as you know Molenaar took his own life after speaking to his partner. So those sorts of things can happen. It's better that things are controlled.
"Now they could put the family member on the phone. Again, things are too unpredictable. It's better to cordon, contain and just sit it out - exactly what they're doing."