"It was probably one of the most stressful situations I have ever found myself in," he said.
Being in a stressful situation is nothing unusual for front-line police, whether it be a domestic-violence situation or a fleeing driver.
But trying to get inside the head of someone who wants to harm themselves, and then talking them to safety was very challenging, he said.
"I guess I've drawn on a lot of experience with a high-risk job on the front line, but yes, there's adrenaline, absolutely. There's no doubt that you go in with intense focus but there's a slight aura of calm around a cop in that situation because you know what your job is and you try to think through things logically and systematically, and just take things slowly and I think that's the key.
"We can't rush them and you can't rush going up to somebody like that."
Talking in general terms, Hannah-Jones said the aim was to try to get to know the person and understand why they were in the position that they are in.
"You try and build some common ground and that's the thing about cops as well, is that we make a living out of talking to people in all sorts of situations and often, when you have a goal or particular outcome in mind, that is the best for everyone involved.
"It takes a bit of skilled communication to get there when someone is not necessarily on side."
However, officers had to choose their words wisely.
"If you say the wrong thing it could change the outcome ... the ultimate decision is made by the person."
Hannah-Jones said his 11 years' experience of being on the front line and dealing with a multitude of highly stressful situations, helped him on Sunday.
"The experience I had on Sunday was unlike anything I have ever done before. In fact it was probably one of the most stressful situations I have ever found myself in, for reasons I guess is only natural, for someone to go through the alternatives in your head and the weight of the decision-making does bear upon you personally.
While front-line officers received training, it paled in comparison to being thrown into a real-life situation.
In general, once a person has been successfully talked down - like on Sunday in Auckland and Monday in Hamilton where two girls were talked down from the roof of a shopping centre - they are taken away by police, given a chance to calm down over a cup of tea, and chat about how they would put one foot in front of the other in the weeks and years ahead.
Making someone change their mind from doing something potentially deadly made the job even more fulfilling, he said.
"It's all hard but it's hugely rewarding, especially when you get the right result for them."
Where to get help:
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906 (Palmerston North and Levin)
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
• Samaritans: 0800 726 666 (available 24/7)
If it is an emergency and you feel like you or someone else is at risk, call 111.
