Genevieve Gyulavary was in her eighth grade maths class when she was told over the loudspeaker to report to the office.
Her mum Jane had called the school to explain that a plane had gone into the World Trade Center, where her husband and Genevieve's father Peter worked.
Jane, now 74, told Genevieve she had spoken to Peter and he'd reassured her that "everything's fine" and he would soon be leaving his 91st floor office in the south tower.
Genevieve, then 13, was driven home and her memory of that moment is vivid and heartbreakingly poignant.
"I remember sitting in the car and it was a beautiful day. There were no clouds in the sky," she tells Woman's Day.
"And then I got home and it was chaotic because my mum now couldn't get in touch with my dad."
Peter, 44, was eventually confirmed to be among one of 10 known Australians killed in the September 11, 2001 attacks.
But in the immediate aftermath, Genevieve and Jane were unable to do much except wait for news.
"There was this lingering hope for a little bit... that he might still come home, because he always did," she says.
Like others missing loved ones, Jane hoped someone would find Peter in the confusing aftermath.
"My mum put a sign on a tree saying, 'Have you seen this person?'"
At the end of October, with all their initial hope gone, the family organised a memorial for Peter.
In a strange twist of fate, the evening before, a policeman came to the door of their home in Warwick, upstate New York and told Jane her husband's body had been recovered.
Twenty years on, Genevieve is grateful her dad was able to return home.
"I would hate to have to go to Ground Zero and the memorial and think that's all I have," she says.
But losing her father at such a young age, and at such a high profile and historically significant event, made Genevieve's loss hard to bear.
"It was already such a public grief," she says. "It was very difficult to process it at that age.
"I didn't talk about it for many, many years. I don't even remember really crying."
Now 33, she still finds the subject incredibly painful.
"If somebody talks about 9/11, it hits me like a gut punch," she says.
"Over the years it's got a little bit harder because I process it more as I've gotten older."
This year, on the 20th anniversary of her father's passing, Genevieve says she will put her phone away and keep the TV turned off.
"It's just too much for me," she admits.
Instead, Genevieve prefers to celebrate Peter, who she says was "not like other dads", not least because he was Australian and had an accent.
"I thought that was really cool," she laughs.
Originally from Geelong, Peter emigrated to the US in the late '70s and was a talented and ambitious environmental engineer, who by 2001 was working for Washington Group International, where he'd recently helped design the St Louis metro system.
"He had this nickname, 'The Bulldog'. He was going places and he was very smart and very well respected," says Genevieve.
"He was also very physical. He was fit and always doing something – he was never sitting still. So I think I'm like him."
Proving she is very much her father's daughter, Genevieve – who lives with her fiance Jacob, 26, an aerospace engineer in South Windsor, Connecticut – has now made being physical her career.
With a doctorate in physical therapy, when the pandemic started, Genevieve decided to follow her dreams and open a cross-fit gym, where her aim is to "rehabilitate, train and educate" clients in functional fitness.
But while trying to decide whether she was making the right decision for her future, Genevieve frequently wondered what her dad would advise.
"I would be like, 'Give me a sign that you think this is OK and a good idea...'" she says.
Genevieve believes that by pursuing her passion, she is honouring her dad.
"At the end of the day, we should all be so lucky to die doing what we love. I think that's what he did," she says.
"I hope he would be happy that I'm following my passion."
Next month, Genevieve and Jacob get married, and the joyous event will be a bittersweet reminder of all the Gyulavary family have lost.
"My dad is never going to meet my fiance and when I get married it's going to be really hard to not have him there," she says.
"I just wish he was here to see me today. He was special."