The partner of a mother killed trying to save her baby from a stabbing at a busy Sydney shopping centre has spoken out for the first time, saying the day of her death will “never make sense”.

Ashlee Good, 38, was among six people killed by Joel Cauchi at Westfield Bondi Junction on April 13. Her daughter Harriet, who was nine months old at the time of the attack, was also injured.

Australian authorities say the stabbing was related to “mental health,” but they believe Cauchi specifically targeted women.

Good’s partner Dan Flanagan thanked donors and said the “overwhelming support, kindness and generosity” his family has received has given them “strength.”

Mass murders are rare in Australia and the attack at one of the country’s largest and most popular shopping centres shocked the world.

Horrified witnesses described how Good desperately fled to a nearby store and sought help for her injured young daughter.

In a post on a GoFundMe page that has raised nearly 850,000 Australian dollars (£439,000; $560,000), Mr Flanagan said the loss of his partner – an osteopath described by friends as “full of life and love” – ​​was “unimaginable”.

“The day our family of three became a family of two will never make sense to me, but countless people … have shown me that while tragic things still happen, there is more good than bad in this world,” he wrote.

“Nothing will ever take away the pain of losing Ash, but reading your messages and seeing the impact Ash has had on so many people has brought me a lot of comfort.”

He also expressed his condolences to other families, friends and communities struggling with the trauma of the attack.

“Our lives will never be the same again and I wish each of you strength and hope that you get the support you need to get through these incredible and difficult times,” he said.

Cauchi stabbed 17 people before being chased and shot by a lone police officer.

In addition to Good, five other people died – security guard Faraz Tahir, 30; Jade Young, 47; Pikria Darchia, 55; Dawn Singleton, 25; and Yixuan Cheng, believed to be in her 20s.

Baby Harriet, the youngest victim, had to undergo surgery to treat her chest and arm injuries in order to survive.

A special task force has been set up to investigate the incident, and New South Wales Police said it could take months to release its findings.

Cauchi’s parents said the 40-year-old suffered from mental illness and had stopped taking his medication shortly before the attack.

Some, including Jade Young’s family, called for immediate strengthening of mental health services to prevent similar acts of violence in the future.