The attributes that helped Jacinda Ardern rise to become New Zealand's leader at age 37 include her optimistic outlook and bright personality. And she became an inspiration to working women around the world last year when she gave birth to a daughter, Neve.

But the prime minister is now displaying other qualities to an anxious nation after a gunman on Friday slaughtered 50 people at two Christchurch mosques. She's shown a determination to change gun laws and a deep empathy with the families of the victims and the Muslim community.

Friday's events where the first major test Ardern has faced since she became prime minister in a contentious general election in 2017.