Gunman Martin Bryant was still at large as Walter Mikac dashed across the Port Arthur Historic Site desperate for news of his wife and young daughters.
Those moments from a day in April 1996 remain vivid for the now 55-year-old whose grief turned to motivation as he built one of Australia's most respected childrens' charities: the Alannah and Madeline Foundation.
"The most immediate thing I wanted to do, the gunman was still at large, was just to run straight out into the site and go with them," Mr Mikac told an audience in Hobart on Friday gathered to mark the 20-year anniversary of the foundation formed in his daughters' names.
"Once I'd seen them, once I'd said my goodbyes, it was very clear that no matter how I reacted, it wasn't going to change the situation."
Alannah, 6, and Madeleine, 3, along with their mother Nanette were among 35 people killed in Australia's worst massacre.
"If I shut myself away from the world or I did myself away, it wasn't going to change that situation," Mr Mikac said.
"There's got to be some reason why I am still here and it took a long time to try and come to peace with that and try and accept what had happened."
The foundation has helped more than two million children since its inception and has the support of international patron Crown Princess Mary of Denmark, and the praise of Prime Minister Malcolm Turnbull.
"We honour its inspirational vision of friendship and good will and pay tribute to the courage and dedication of its founders, most especially Walter Mikac," Mr Turnbull wrote in a statement.
"No one could have done more to honour the memory of their children and to prove that great good can come from terrible tragedy."
The foundation offers a domestic violence support network for children, runs a series of anti-bullying campaigns and its latest project is a program to combat cyber bullying.
For children who have to leave home in a hurry the foundation provides a Buddy Bag, filled with essentials like a toothbrush and pyjamas.
Thousands of the bags have been distributed.
Mr Mikac, who was speaking publicly for the first time in Tasmania since the shooting, said the foundation's success helps bring him peace.
"I had been lucky with Nanette and with the children to have experienced and incredible amount of love.
"To know that day after day their names are being remembered helping other children live better lives, lead more protected lives, hopefully saving them from being exposed to violence ... I'm going to put my weight 100 per cent behind that."
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