Most people of a certain age can remember where they were when the Twin Towers were attacked on September 11, 2001.
And President George W. Bush is certainly no exception.
On the historic day, President Bush was visiting an elementary school in Sarasota, Florida, where he was sitting in on a reading class.
When he first arrived at Emma E. Brooker Elementary School that morning, he'd already been informed that a plane had hit the World Trade Center - which Bush said he thought was a 'pilot error'.
The true scale of what was unfolding wouldn't be known until he was inside the classroom - and the devastating moment was caught on camera.
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As the President prepared to begin reading The Pet Goat with the students, the White House Chief of Staff Andrew Card came over.
He then leaned in and whispered to the President: "A second plane hit the second tower. America is under attack."
Card later reflected on the moment when he had to tell the President of the horrifying attack.
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Speaking to Sky News in 2021, he said: "I looked at the president and I honestly believe he was thinking about the burden that he accepted when he took the oath of office.
"I like to say that's when he became the president."
After hearing these words, President Bush remained sitting down and participated in the children's reading exercise for a further seven minutes.
Later, he would learn the full scale of the tragedy - with more than 3,000 people having tragically lost their lives on that historic day.
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Card continued: "I was very impressed that he did nothing to introduce fear to those students.
"He did nothing to demonstrate fear to the media that would've satisfied terrorists all around the world."
President Bush also reflected on the moment himself in a 2021 BBC documentary, 9/11: Inside the President's War Room.
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He said: "Andy Card comes up behind me and says, 'Second plane has hit the second tower. America is under attack. "And I'm watching a child read.
"And I see the press in the back of the room beginning to get the same message that I just got.
"I could see the horror etched on their face of the news people who just got the same news.
"And so I watched for the appropriate moment to leave the classroom.
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"I didn't want to do anything dramatic, I didn't want to lurch out of the chair and scare the classroom full of children.
"And so I waited."
If you've been affected by the contents of this article you can find more information and support at the VOICES Center for Resilience via their website.
Ben Thompson