She amputated his legs with a pocket-knife and hacksaw as the aftershocks continued.
On the afternoon of February 22, urologist Lydia Johns Putra was on a lunch break with a group of other doctors who had gathered for a conference at Christchurch's convention centre.
A brisk walk away, financial adviser Brian Coker was in the Pyne Gould building and was also going to head out for lunch.
He was on the first-floor landing and about to go downstairs, when he was showered in tiles and debris as the quake hit and he was swept off his feet by a cascading concrete wall.
Coker immediately knew he was trapped, he said so in statement a few days after where he detailed exactly what he was thinking and what he did.
Coker was in excruciating pain and tossed up whether to message his wife Helen, he did not want to worry her but he did want to tell her that he loved her and may not survive.
She got his text at 1.03pm and then called the police, telling them what Brian looked like, what he was wearing and where he was.
Johns Putra and some of the other doctors had arrived at the collapsed building. She spent some time watching emergency services work and told them she was a surgeon.
By this time Coker was wishing for a decent aftershock to finish it, but it was also when Johns Putra, another doctor, a firefighter, a police officer and a team of rescuers were making their way towards him.
Johns Putra said they ended up going through the building and up the collapsed stairwell to get to him.
"There wasn't much space at all as you can imagine, it was collapsed and it was dark and a few regular aftershocks and so it was quite cramped."
She said they were initially able to walk but ended up having to crawl to get to the spot they needed to be at.
Coker, who had concrete dust in his nose and mouth, remembered being given a drink of water and later morphine.
He could hear other people screaming in the building.
When rescuers returned about 7pm that night, they cut his trousers and told him he was coming out.
"We had an anaesthetist as part of the team so that was very important," Johns Putra said.
"This is not an operating theatre, this is a field procedure and so we had tourniquets which reduces the blood flow which is important, we had a knife and we had a saw and when you think about it a knife and saw are what you would use in an operating theatre but that's what we had."
Johns Putra said she does not recall where the hacksaw that she used for the amputation came from, but thinks someone gave her the knife which was also used.
"When you're focused on a job to do, it's not that tough when you have the end goal in mind, I don't recall it being tough in the mental sense, clearly the physicality was challenging, but working in this incredible team and collaborating towards this goal.
"The end point was to save and rescue Brian."
She said there were certainly physical challenges and while doing the amputation she had to lie on the ground on her stomach.
"It was dark and it was cramped and it felt like rubble on the ground and we talked about the shocks as well."
She said she does not remember dwelling on the discomfort though because the end point was to save someone.
Johns Putra said she does not recall being scared at the time.
"There's definitely the focus and there's the energy and the adrenaline of what you have to do and needing to get through what you need to do to what you need to achieve."
After the operation Coker was rushed to hospital and Johns Putra was able to leave the Pyne Gould building, going to the park to find her colleagues and friends.
She said she does not recall thinking she did not want to enter the Pyne Gould building that day.
"I think that something needed to be done, I had a small skill that was helpful."
Johns Putra said so many people did so many things that were helpful on that day.
She said many people were brave on that day.
"Those poor people themselves who were there, they didn't ask for it, and I watched all these incredible people do things, and continue to do things."
Johns Putra got a bravery award for what she did that day, so did the others involved.
Her official citation tells the part of the story that she does not.
Coker was in danger of bleeding to death, pinned between a pillar and a collapsed section floor and there was no other way to get him out.
She started cutting his legs off with the hacksaw but the job was so tough at one point she was too tired to carry on and the saw was passed to the other doctor, the firefighter and the police officer, to all take turns.
Coker survived because of them.
Johns Putra said the experience changed her life.
"This is a life-changing event for the people of Christchurch and New Zealand and Christchurch as a city itself, so for me it's a pivotal moment for me. I've learned so much that has changed me in conscious and unconscious ways I'm sure, of course it's changed me."
Johns Putra continues to work as a urologist and she has been in contact with Coker and others who were part of his rescue since.
