(UVALDE, Texas) -- On the morning of May 24, Eva Mireles, a mom who loved karaoke, hiking and working out, texted her daughter about a CrossFit backpack she planned to buy.
Her only child, 23-year-old Adalynn Ruiz, texted back.
And that was the last conversation the close mother-daughter duo had.
Hours later, Ruiz heard about a shooting at Robb Elementary School in Uvalde, Texas, where her mom was a fourth grade teacher.
Ruiz kept calling her parents, but they didn't pick up.
"I wasn't really freaking out about my mom -- I was freaking out about my dad," Ruiz told ABC News' Maria Elena Salinas on Monday in her first interview since the massacre. "One of my worst fears was an active shooter, since my dad is ... an officer. That's what scared me the most."
Ruiz's father, a school district police officer, responded to the scene of the mass shooting. Once her dad called back and told her he was OK, Ruiz said a "huge weight lifted off my chest." She chose not to discuss the law enforcement response at the school, which remains under investigation.
But then Ruiz learned her mom had been shot, and she broke down.
"My coworker drove me home to Uvalde, about an hour. It felt like the longest drive ever, just waiting and waiting," she said. "I texted my mom and said, 'You're gonna be OK, Mom, I love you so much.' And that's the last thing I sent her before I found out she didn't make it."
Mireles was among the two teachers and 19 children gunned down at Robb Elementary School.
"It's hard when the person that did everything for you, did everything with you, is not here anymore," Ruiz said. "It's hard to go on without her."
Mireles was a dedicated fourth grade teacher who "always wanted to make sure that her students were happy and taken care of," Ruiz said, remembering how her mom's young students would run over for a hug when they'd see her around town.
Ruiz later learned that her mother was killed while trying to protect her students from gunfire.
"I know she didn't even hesitate to step in front of [her students]," Ruiz said.
Ruiz added, to her, Mireles was a hero long before that day.
"She was dedicated to her job ... she was strong. I just really hope to be exactly like her," Ruiz said, adding, "My dad has always been my hero, too."
In the wake of the massacre, which was carried out with an AR-15-style rifle, Ruiz said she hopes to see stricter gun laws in Texas, calling assault weapons "guns of war."
"We should be the last family to have to go through this," she said. "This should be an eye-opener to a lot of people. Who's next, you know? Whose family is gonna be next if this doesn't stop?"
Ruiz is now channeling her energy into helping plan the Remember Their Names festival, set for Oct. 30, to honor the Uvalde victims and survivors.
The festival will be filled with food, music and personalized events to recognize each lost life. In honor of Mireles, there will be a karaoke contest, Ruiz said.
She said the festival proceeds will go to 22 scholarships, one to represent each victim and one in recognition of the survivors. The families of each victim will get to choose who will be awarded the scholarship based on applicant essays.
The families hope to make this an annual event, Ruiz said, "to make sure nobody forgets."
As she looks forward, the 23-year-old noted, "I'm gonna have to miss my mom longer than I've known her. ... I still have the rest of my life, and how am I supposed to do that without my mom?"