Transcript for Students across the country rally in National School Walkouts to end gun violence
It's dawn in parkland, Florida. An important day at school for freshman Brooke Harrison. The ritual of routine altered. A ribbon to remind what's ahead. A new backpack to replace the old one and the horrors associated with it. There was a bullet hole in my backpack. Now that's going to be forever with me. And that's like forever going to be like a memory. Reporter: A memory that pushes her through the pain of the past into what she feels is her new purpose. Doing the walkout today for really Alaina, one of my friends that was lost, where she used to sit at lunch it was like usually the same spot. So I remember walking past that place. I remember like thinking like I'm never going to pass by her again, never going to be able to like sit with her again. And that just hit me so hard. Reporter: Today marks a grim anniversary. One month since the shooting at Marjory Stoneman Douglas high school that killed her friend Alaina petty and crushed this community. She and fellow classmates are preparing to walk out of their classes. Joining students from more than 3,000 schools across the country. Never again! Reporter: Who are demanding change. We're all here. We're all gathered together to show that we care, to show that we have voices, we're young people and we're passionate about what we have to say. Reporter: From Chicago. Our voices demand change. Reporter: To Little Rock. We just want to end gun violence. We should come to school to learn and not to lose our lives. Reporter: To Denver. It's time to wake up. Reporter: And countless other towns and cities in between. Students walked out of their schools today at 10:00 A.M. A 17-minute walkout. Now! Reporter: One minute for every life lost. I love you. I love you. Reporter: But in parkland today is much more personal. I'm doing this walkout for Joaquin. And that's just about it. Why should we be expected to learn when these politicians aren't going to do their job? Why should we as students? Reporter: For Brooke and so many others time stopped on February 14th. It seems like it was just yesterday. Reporter: She was in the very first classroom the shooter came to. Of the 17 people murdered three were in her classroom. We were the warning shot for everyone else. But we didn't get a warning shot. Reporter: Brooke remembers in the chaos trying to hide behind a desk. I remember someone telling me there's not any more room and then I was being pushed back. I mean, we were in a drastic situation. That's where Alaina was. And I remember making dead eye contact with her. We didn't even have words because I don't think in that moment either of us could find any. And the last thing I remember, like the last vision I have of her was her actually hugging someone. It's just a miracle that Brooke is alive. It's where she ran to that day. It's the angle of the bullet that just missed you. Reporter: Brooke and her family were later interviewed by the FBI. Brooke and four other girls recreated a@ diagram of where everyone was sitting. Alyssa alhadeff was right beside the teacher's desk and she died. Alaina petty was by the teacher's desk and she died. Zblefrn arou Everyone around me was either grazed or shot or killed. I don't -- it doesn't make sense. Reporter: Today Brooke says her place is back where it all began, at school. I want to make sure that no kid my age ever has to see what I have to see. Reporter: As she and her mom head out, all around them they see an outpouring of love. We've had just so much support and so much love from all of this that I didn't feel like as hard as it probably would be if we didn't have the community we have. Have a great day. Reporter: For Denise that sense of normalcy no longer exists. That's all you're thinking about every day when you drop your kids, please let them be safe for the day. Reporter: She's constantly on guard. When you're seeing kids walking in with your backpacks, you think anything could be in those backpacks. Three people shot. Three people shot. Three people shot! Oh, my god. Reporter: Newly released 911 calls retelling those terrifying moments in the classroom. As students place frantic calls for help. Please, please, please. There's people here. They're all bleeding. They're going to die. Reporter: Dispatchers trying to comfort the inconsolable students. I'm not going anywhere. You stay on the phone with me. We're at the school. You stay on the phone with me. Done hang up. Just be quiet. Reporter: Earlier today Nikolas Cruz, the alleged gunman, was formally arraigned. Mr. Cruz, you've been charged by indictment. In count 1 of the indictment with murder in the first degree. Reporter: Cruz, head down, stood mute as he faced tearful parents of the victims. A plea of not guilty shall be entered on the defendant's behalf. Reporter: He's charged with 17 counts of premeditated murder. 17 counts of attempted murder. His lawyer saying he would plead guilty if the death penalty if off the table. The response to the shooting and how Cruz was able to carry it out despite numerous warning signs about him was the subject of hearings on capitol hill today. The man did anything but take an ad out in the paper I'm going to kill somebody. Reporter: Testifying before the senate committee, Alaina's father, Ryan petty, fighting back tears. The senseless murder of so many including my own beloved daughter Alaina tests the limits of faith. Reporter: Pleading for common ground. We do not have to all agree on guns, and we won't. But we can agree on the most fundamental things. We can agree that students and teachers should be safe. Reporter: Outside, local students protested, turning their backs to the white house. But despite their efforts, it's unlikely that Washington lawmakers will take action on gun control. After president trump initially expressed support for some gun control measures. Some of you people are petrified of the NRA. You can't be petrified. Reporter: Earlier this week on Twitter he walked back on federal restrictions pushing the decision instead to the states. One place where change is already under way, Florida. Just last week governor Rick Scott signed a law both increasing funding for school security and also raising the legal age to buy any gun in the state to 21. The NRA has filed a federal lawsuit trying to block the age restriction, saying it violates the second amendment. The new law also creates a voluntary so-called guardian program, allowing some teachers and other school employees to carry guns in school if they complete law enforcement training. And while many students are focused on change, others in parkland aren't quite ready to become full-fledged activists. Like Dylan mccootie who lost his best friend Joaquin Oliver and guac's girlfriend Martina Gonzalez. I want to be a voice heard, be a change, but it's kind of hard to. Can't be as loud as I want to be right now. So I'm not going to step there yet. But I definitely plan to. Reporter: For junior Dylan Kramer just going to school has become a daily struggle. Like when I'm sitting in the classroom I stay away from the door. If this happened again what would I do? Where would I be hiding? Sometimes it plays back in my head and it keeps me from -- it like scares me to go to sleep. Reporter: Dylan was in history class when he says he came face to face with the gunman. I saw him like turn one way and shoot that way and then turn the other way and shoot that way and then turn to my classroom and that's when I like saw down the gun barrel and I like saw his eyes. I saw bullets flying into my classroom, hitting the wall. Going past my head, hitting computers, hitting the computer cart, and then hitting a couple kids. Just thinking like I was going to die pretty much. That was all. I just waited. And then he moved on to the next classroom and I was still alive. Reporter: And for those who walked away with their lives, today they walked out not in fear but in confidence. Marching by the thousands out of their classrooms and onto the school football field. Parents and families showed their support from a distance. Then instead of going back to class hundreds of students continued on to pine trails park, where they huddled around memorials for each of the 17 lost. There the emotional weight of this day poured out in tears and outrage. We're not just kids anymore because we looked down the barrel of a gun! We're not kids anymore because our friends and our teachers and our coaches died. We are here as a family because we want something in common, and it is change. All of us are msd strong and we're going to stay msd strong and we're never going to let it happen again. Reporter: Never is a word we've all heard before. This time does feel different. Words centuries old remind us as we look into these young faces. A child shall lead the way.
This transcript has been automatically generated and may not be 100% accurate.