In the wake of the Christchurch massacre, stunned residents were looking for images of hope.

They found it in a photograph of prime minister Jacinda Ardern, clad in a black headscarf and overlaid with flowers reflected on the glass outside.

She is listening with clasped hands to the Muslim community in Christchurch, not 24 hours after 50 of their number had been gunned down by an alleged terrorist. Her face attentive, compassionate. On New Zealand’s “darkest day”, she was showing its best qualities.

The photo was taken by Christchurch city council photographer Kirk Hargreaves at the Phillipstown community centre at about midday on Saturday.

Ardern had just flown into the city along with the leaders of other political parties and a contingent of Wellington media. She went straight to the community hub to meet representatives from the Muslim community.

They gathered in a small, converted classroom. Hargreaves, formerly with Christchurch paper The Press, arrived late and could not get inside.

“That’s how I got to be outside taking that photograph,” he said. “It certainly wasn’t a good feeling to be stuck out there by myself not getting any imagery.”

Hargreaves tried to photograph the meeting through the window but the glare from the sun meant he couldn’t see through. Then Ardern stood up, and he could see her face through the glass.

The full image of Jacinda Ardern. Photograph: Kirk Hargreaves/Christchurch city council

“I couldn’t actually photograph her at first because there was so much reflection,” he said. “So I tried to put on a filter which is called a polarising filter … it didn’t work but I just thought ‘oh, bummer, I’ll leave it’.

“But then I found this kind of angle to photograph through … and I was then starting to get hit with her amazing body language and then all the reflections of the flowers and trees outside had done this incredible stuff … the whole thing was such a blend of different religions as well as her incredible body language and I thought: I have just got to get these pictures.”

The image was uploaded on the council’s Facebook page and has been widely shared across both social and traditional media as a defining image of Ardern’s leadership.

In a bleak period in the city’s history, Hargreaves said the image is one of hope.

“When I took it I was so moved by the humanity,” he said. “I probably didn’t know how well it was going to go, but as a photographer I knew that this was a cranking shot. It just sums up what she’s doing, how she’s offering her humanity in a way to those people and she’s listening, she’s concerned, she’s loving.”

He said the image would be interpreted in the same way in “any religion, any culture in the world”.

It is not just Ardern’s stoicism on display: also in frame is the face of James Shaw, the co-leader of the Green party, sporting a black eye from being punched by an angry voter as he walked through Wellington.

“When they came out of that room I was amazed at the way all the politicians, the leaders, they were all jamming on the same page, they were all in it together,” Hargreaves said. “It wasn’t just her … it was such an example of what people should be looking for in their leaders.”