NEW YORK (PIX11) — On the morning of Sept.11, 2001, the sun cast its final glow on the iconic twin towers; within a two-hour period, hijackers carried out the deadliest terrorist act in world history.

“Everyone remembers that clear blue sky day, and I remember thinking everything would be OK, because my brother John was a MacGyver of sorts,” said Anthoula Katsimatides, of Queens.

By day’s end, Katsimatides and her family knew they’d never see John again.

“Once we realized the night had passed, we realized he wasn’t coming home. We held out hope for a month, but we had to come to that realization,” said Katsimatides.

John, 31, was working in the towers on 9/11 as a bonds broker for Cantor Fitzgerald. Twenty-one years later, loved ones of the nearly 3,000 innocent lives lost continue to unite at Plaza Memorial to commemorate the fallen.

“What a lot of people don’t understand is that for some people, it’s the days leading up to 9/11 or the week of 9/11, because there’s so much press and everything’s, you know, reliving that, but for families, it’s an everyday thing we live through,” said Bea Woolen.

Woolen’s sister, Tamara Thurman, was a sergeant for the Department of Defense. She was in the Pentagon at the time of the attack.

“Very close in age, we grew up together, two peas in a pod, when you saw her you saw me,” said Woolen.

Following the tragedies, Woolen holds the memory of her sister close to her heart. Like so many others, Katsimatides promises to be a better person in memory of her beloved brother.

“I miss him so much and I wonder what life would have been like if he was here, but I promised him every day that I will live the biggest and brightest and fullest life I can,” said Katsimatides. “No matter how many years have passed, what happened to my family and all these families, to the nation and world is something that should never be forgotten and I think it would be a tribute to the lives lost if we lived with more compassion and love in our hearts.”

As families remember their loved ones, members of the National September 11 Memorial Museum want to make sure people continue to visit, so future generations are reminded of this painful day and to never forget.