For the younger generations, it's now also a heart-wrenching history lesson.
When thinking about September 11, 2001, most can recount in detail where they were, what they were doing, and how they felt the moment the nation was attacked.
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That day's devastation is what reinforced now-Deputy Fire Chief Aaron Freyler's decision to enter the San Jose Fire Department (SJFD) academy that same year. Instruction started just one week after the deadly attacks.
"We just watched, not just people give their life, but you know, their whole support staff and everyone around them just gave it everything they had that day," Deputy Fire Chief Freyler told ABC7 News.
Today, after 20 years with SJFD, Deputy Chief Freyler said every day is dedicated to those killed in the attacks and beyond.
"It's a lot of weight to put on the shirt and this badge every day, knowing it's not just them you're trying to do proud," he said. "But also their families. And of course, also the other people they've helped along the way."
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The 20th commemoration on Saturday holds deep meaning for him, as 9/11 remains a vivid memory. Deputy Chief Freyler added, the day will bring him a sense of reflection.
Thinking back to his time in the military and about his transition to SJFD, Freyler shared, "You're out there every day knowing you're playing a part for something much bigger. Just knowing that you're servicing a community as a whole- which is great in the military. After I did my four years, and wanted to keep that feeling of service going."
However, September 11 initially meant something different for new SJFD Firefighter Tayler Peters.
Firefighter Peters graduated from the academy on September 3. She admitted having little recollection of the 9/11 attacks. Back then, she was only four-years-old.
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"I just remember my mom sitting in our dining room chair, staring at the TV and crying," Peters recalled. "I knew something was different, but I didn't know exactly what."
The daughter of a retired Hayward Fire Department Captain, Peters said her dad's unwavering dedication to the fire service following September 11th was both eye-opening and educational.
Peters said, "Seeing how he went to work in the years after 9/11 really had an impact on me, and also led me to see that firefighters were really impacted by this event."
Adding, high school history lessons on the attacks drove home the desperation.
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"That was probably the moment when I realized, this is a big deal," she told ABC7 News. "And from then on out, learning about 9/11 was important for me."
"Especially being the 20th anniversary, I've learned a lot recently. And I think that has helped me really respect those firefighters that went in, and respect what happened," she continued.
As SJFD prepares for its 2021 Patriot Day 20th Year Commemoration on Saturday, Peters added what the day will mean for her, as she reflected on the men and women in the fire service who responded that day.
"The sense of bravery that they had is incredible to think about, and I think that's what's gonna sink in for me tomorrow," she told ABC7 News.
Today, the attacks are still certainly shaping and inspiring generations of first responders- those who lived through it, and others who are learning about it.