Sandy Hook survivor Emma Ehrens in 2023 speaking at National Vigil for All Victims of Gun ViolenceSecond Gentlemen Doug Emhoff

On the eve of her high school graduation, one Sandy Hook survivor is revealing her growing guilt as she vividly remembers the day that "really took a lot of her childhood."

"I've been feeling a lot," said Emma Ehrens, who survived the horrific attack on the Connecticut elementary school 12 years ago.

"I have thought about... if I'm not doing something big, did I survive for the right reasons?" She spoke about the survivor's guilt she has felt her entire life.

Emma and another surviving classmate, Grace Fischer, are bracing themselves to hear 20 other names of former classmates who never got to leave the first grade with them.

"It's just going to be heartbreaking," Grace told CNN. "I can't imagine that 20 kids are not graduating with us and that they're not having the opportunity to walk across the stage."

Emma revealed she's preparing herself for a range of emotions she expects to feel, including the joy of graduating, nerves about the future, and contemplating what should have been.

"Thinking about all the what-ifs: what if they were sitting next to me at graduation? What if we were still friends? Where would we be? It's just going to be a lot of what-ifs in my head," she said to CNN.

"I really want to make sure that they know I'm doing something," Emma said of her classmates who lost the chance to graduate.

"Even though they're not here anymore, there are people who survived who are really trying to push for them. Because their lives were lost so early and I went through that at such an early age, I feel like it's my purpose to continue my life in honor of them," added the soon-to-be-graduate.

Emma was six years old when the Sandy Hook massacre happened. She had been looking forward to making gingerbread houses when the 20-year-old gunman, armed with a semi-automatic assault-style rifle and two handguns, shot his way into the school.

It's when the students were led to safety and lined up by grade that they noticed half their grade was missing.

"I'm graduating, I'm going to college, I get to go home, I get to see my dog, and I get to do all this when they don't. It's just really hard."