The first thing Andrea Peña did when she got home was sit at her piano. She had just spent nearly two hours huddled with 60 classmates in an overheated drama classroom closet while a former student, armed with a rifle, opened fire on their high school, killing 17 and wounding just as many. Peña needed to feel something — anything — other than numb. So she put her fingers to the keys and played.

Jennifer Linn’s “Rainbow Prelude” was the obvious choice. She had recently played it for a piano competition and the melody was still stuck in her head. She poured herself into that song, letting the music take over. She was angry, pounding on the keys, until she reached the softer part of the composition. That, she said, made her feel hopeful again.

The high school sophomore has been playing piano since kindergarten. She picked up a guitar three years ago. And she’s been singing for as long as she can remember. Music is more than a hobby.

“When I'm upset about something, or when I'm mad, I play the piano, or the guitar, or sing. That's just what I do," Peña, 15, told MTV News. "It's a sense of relief. That's how I deal with my emotions."

So, in the aftermath of the Feb. 14 school shooting that ravaged Marjory Stoneman Douglas High School in Parkland, Florida, that's exactly what she and her fellow drama classmate, Sawyer Garrity, 16, did. They played. And gathered a few days later at Peña's house, as some of the very same MSD drama students who survived that cramped closet painted (because "art is a good release") to the sounds of Garrity's favorite Glee playlist.

The painting sessions were therapeutic but by Saturday, Peña knew she wanted to do something more. But she wasn't comfortable speaking to the press like some of her more outspoken MSD peers, and she didn't feel well-versed enough in politics to jump into the #NeverAgain fight spearheaded by her fellow drama classmate, Cameron Kasky. So she spent hours distracting herself at the piano — until she received a text from Garrity, who'd been feeling similarly restless: "We should write a song together."

That, Peña could do. Or at least she believed she could do it. She had never composed her own music before.

"I was thinking, 'We're definitely never going to do this,'" Garrity recalled. "And then 10 minutes later, I get another text message from Andrea, and she was like, 'So I was thinking this for the piano.' And she then sent me a voice memo of her playing."

A few minutes later, Garrity sent Peña the first verse of what would eventually become MSD's uplifting anthem, "Shine," beginning with the lyric, "You, you threw my city away." Garrity's moving words, Peña said, motivated her to create even more music. So, they began feverishly sending each other voice memos. Garrity would sing part of a verse, and Peña would send her more piano chords. They met up on Monday to finish it up. "We finished the song in half an hour," Garrity said.

Garrity sent the demo recording to their drama teacher, Melody Herzfeld, "because I just thought she'd want to hear it," she said. So she was surprised when the song brought her teacher to tears. "We were like, 'OK Herzfeld, it’s not that good,'" Garrity said. But they had underestimated how cathartic the words "you’re not going to knock us down, we'll get back up again" would be for a community reeling from so much heartbreak — and for a campus in the midst of a gun control revolution.

After complimenting her students' "beautiful piece of music," Herzfeld then shared the song with Florida Congressman Ted Deutch's office. The next day, Garrity received a call: CNN wanted them to perform the song during the network's televised town hall on gun control on Wednesday — as in, in less than 24 hours. "I was like, 'What? No! We can’t! It’s not done,'" she said. "I was having a mental breakdown."

But after an afternoon of rehearsals, in which Peña had to track down a second piano after she left hers at the venue, and some help from some of their drama friends, who all had to learn the song and their spoken-word parts the day-of, Garrity and Peña were ready. Or as ready as they were ever going to be.

"The last rehearsal wasn't the best, and I was really nervous when I found out it was going to be televised," Peña said. "But when we were up there, I felt a click. We all were in sync. It was the best I had ever played it, and it was the best me and Sawyer had ever sung it."

They had no real plans for the song. They just hoped that a few students and faculty members would hear it and find comfort. But that night, surrounded by the grieving faces of their community as they wept listening to their song, the duo were completely overwhelmed by the response. "For me and Sawyer, not only was this song a way for us to heal, but it was also for the victims," Peña said. "We got to be a voice for those who didn't have one anymore. That's what the song was about."

Though, they also acknowledge that the song shouldn't have needed to exist in the first place. "We never should have sat down to write this song. The shooting at our school should have never happened," Peña said.

"My dad always tells me, 'It’s not what happens to you; it’s how you react,'" she added. "And I’ve been living through that. What happened was tragic, and there were days when I didn't want to leave my room because I was so sad, but that song was such a powerful way for me and Sawyer to come together and show everyone that even though this happened we can, and we will, remain strong."

Now, they plan to release an official studio version of "Shine" ahead of the March For Our Lives rally in D.C. on March 24. The proceeds will go to #ShineMSD, a student-led nonprofit that the girls are working on. Their mission: to inspire healing through the arts and encourage those working through trauma to find a creative outlet for their pain.

At the time of the shooting, Peña, Garrity, and their drama class were rehearsing the department's annual children's show in the auditorium. Their production of Yo, Vikings! was supposed to open March 1, but it's been postponed to a later date. In the meantime, Garrity's rehearsing for the local BARCLAY Performing Arts production of Spring Awakening, in which she's starring as the lead, Wendla Bergmann, opposite her friend Kasky's precocious teen radical, Melchior Gabor.

As such, the Spring Awakening soundtrack has been on heavy rotation for Garrity, in addition to the original Broadway cast recordings of Next To Normal and Dear Evan Hansen. "'You Will Be Found' has been on repeat, she said. "I listen to a lot of musicals. All the musicals in the world, I’ve probably listened to every single one."

She's also writing more music. "I write songs all the time," she said. "Writing is my outlet. Some people will call a friend and rant to their friend; I’ll pick up my guitar and rant to my guitar." Her latest: an original called "Back To You," written for the friends who have been there for her when she needed them most these past few weeks.

"This thing made me realize that if I have a lyric in my head, just write it down," Garrity said. "You have to live life to the fullest, and you have to take advantage of every little idea you have and every little thought you have because you never really know what’s going to happen."

For Peña, the theater is a liberating place — free of the minutiae of everyday teen life, like stressing over homework and science tests. "Practicing and being in drama and running our numbers, and not having to worry about school for just a couple of hours, is a way of escape," she said. "Through the part I’m playing, I get to be whoever I’m playing and pretend to live in their world."

"I feel like when we're on the stage that nothing is wrong," Garrity added, "that everything is back to normal for a second."

Or, in the words of Next To Normal's anxious teenage heroine, something next to normal would be OK, too.

For five ways you can take action on gun violence, head over to enough.mtv.com.