This story was originally published on the one-year anniversary of the shooting

(CNN) As the one-year anniversary of the worst day of her life approached, Hayden Korr grew anxious.

Korr was a senior at Marjory Stoneman Douglas High School in Parkland, Florida, when a gunman stormed the campus on February 14, 2018, killing 17 people.

Barely a day goes by when she doesn't think about it. But as the anniversary approached, flashbacks invaded her dreams and waking hours.

Her friends expressed similar anxieties, she said. They had spent the past year working through their grief. Now, it felt as if they were right back where they started, one year ago.

"We're still struggling and it's still fresh to us," Korr said. "The events of that day are so vivid in my mind that I can't even imagine that it was one year ago."

Students, parents and teachers reflected on how their lives have changed over the past year, and shared their hopes for the future. These are some of their stories:

Loud noises trigger them

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Korr was taking a psychology test when the fire alarm went off. She evacuated to a garden where she heard what sounded like metal banging on metal.

Now, she knows the sound was gunshots.

Loud banging still triggers her. She avoids crowds when possible, and when she's in public she's on high alert, fearful that another shooting could break out.

"The part of me that felt safe to go out has been lost."

Two weeks after graduation, she left Parkland for college in Tampa. But trying to start fresh while she was grieving became overwhelming.

She told people she was from near Miami to avoid questions that would force her to relive the massacre, like if she knew the victims. "I still get choked up today thinking about them."

She made the four-hour train ride back to Parkland nearly every weekend because she was so homesick, then was diagnosed with post-traumatic stress disorder in November and began seeing a therapist.

Living away from home became too much to bear, she said, and she returned home six months later to be closer to family and her therapist.

She is learning to unburden herself through writing, photography and art projects. Some of her work was included in the new book , "Parkland Speaks."

She has enrolled in a new school closer to home, Florida Atlantic University.

She said the healing process continues this week, and the next one, and the one after, and so on. On February 14, she intends to get a tattoo of 17 sunflowers in a vase modeled after Vincent Van Gogh's paintings. Then, she plans on attending a candlelight vigil.

"The past year of my life has felt like a fever dream. It feels like I'm running on autopilot and someone else is controlling all my emotions and actions for me."

Some transferred to other schools

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It's been hard for Kelsey Friend, 17, to shake the sound of the gunshot that ended her favorite teacher's life one year ago, so much so that she decided to leave Stoneman Douglas this month.

As gunshots rang through the hallways, Friend said geography teacher Scott Beigel led her into a classroom and closed the door behind her.

"I heard the shot that killed him. Remembering that bang, it haunts me."

She said she was diagnosed with PTSD last year and she started considering transferring.

Last week, she decided with her mother and school officials that it was best for her to leave. She started classes at Coral Glades High School on Monday.

"It's hard to put into words how much I'm hurting," she said. "It's not that I don't feel safe at Douglas; I don't feel I'm at my best at Douglas."

Part of her struggle, she said, has been accepting that her life will never be the same, and helping others understand that she's still working through the trauma.

"It's hard for people to see that, that I'm still going through things."

Sometimes, they struggle to stay motivated

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In the weeks after the shooting, as Stoneman Douglas senior Hannah Karcinell bounced among funerals and protests, she channeled her grief through activism.

Now, as a freshman at the University of Massachusetts Amherst, she said she continues to find her voice through political engagement.

She has continued to participate in campaigns organized by March for Our Lives, the gun lobby movement that Stoneman Douglas students launched in response to the shooting. She's trying to organize a Change the Ref event on her campus this year to discuss strategies for promoting gun reform.

Activism gives her hope the massacre will lead to changes that decrease the chances of another school shooting. But any time another school shooting occurs, it brings her back to February 14, 2018, and her hopes dim.

"It feels like everything we're doing isn't making a difference, and that nothing will ever change. It can be hard to stay motivated."

Other times, they pretend they are not hurting

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It's been hard for Stoneman Douglas senior Kai Koerber to watch his friends and classmates struggle with depression and PTSD over the past year. As the anniversary approached, anxiety levels appeared to rise, he said.

Koerber said one of his friends told him that he recently tried to kill himself. And Koerber worries about the long-term impacts of the antidepressants his peers are taking.

"We are unable to escape the triggers that are the source of our PTSD."

"Every day, we look at the building where the shooting happened, see gardens filled with flowers for healing and pretend we are not hurting. We walk the halls with our emotional, mental and physical scars, trying to be normal."

Stoneman Douglas has a wellness center that students are encouraged to use, but Koerber said few people want to be seen there for fear of being perceived as struggling.

"People do not believe that mental health is an issue beyond the actual 'crazy' people that commit these acts of extreme violence and mass murder, when in truth it is an issue that affects people both directly and indirectly."

Over the past year, Koerber has found purpose in advocating for mental health curriculums in schools, including Stoneman Douglas. He created the nonprofit Societal Reform Corporation to promote mindfulness-based cognitive therapy programs, such as meditation and yoga, in schools instead of traditional therapy.

He also advocates for emotional intelligence workshops in schools that teach people how to handle interpersonal relationships through coping techniques and conflict resolution.

"I am dedicated to helping my peers and my generation empower themselves. If we are to change the world, we must first manifest that change within ourselves."

They want change, and they want it faster

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Stoneman Douglas American history teacher Greg Pittman has gone from sad to angry to depressed in the past year. Now, he's just upset.

He channeled his frustration into seeking accountability for the massacre and speaking up for the kinds of changes he believes will prevent another one.

He attended school board meetings, participated in voter registration campaigns and shared his goals for stricter gun control measures and improved school safety with anyone who would listen.

So far, though, he's disappointed in what he considers a lack of progress and a lack of respect for teachers' opinions and needs.

"Most of us would probably quit if we could because we're very frustrated at the lack of help that we've gotten."

The Marjory Stoneman Douglas High School Public Safety Act, passed in 2018 , toughened gun control in some ways, but Pittman wants to see more action from the Florida Legislature.

He's also disappointed with Broward County Public Schools' response to a report detailing the missteps that led to the shooting.

Three Stoneman Douglas employees were reassigned to other posts. Pittman wants to see more resources devoted to training, programming and infrastructure that will improve school safety, changes he said would benefit the school more than what he described as "politically" motivated staff changes.

The school district did not reply to CNN's request for a response to Pittman's comments.

"I don't know how long it's going to take for the school to heal," he said.

"It's the teachers that have been keeping the school going and right now they're really holding it together."

They've become activists

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When the shooting jolted Parkland students into action, some Stoneman Douglas parents found themselves raising activists

Initially, Michael Macleod worried about how his son would balance school and activism. Jack Macleod and his friends started Students for Change, a group dedicated to empowering student leaders around gun violence and school safety. Suddenly they were juggling college entrance exams with media interviews and research for their nonprofit.

Michael Macleod said he was relieved to watch his son stay the course on all fronts.

"It's incredible to see how your child transforms from high school student to adult in an instant, jumping into action to do his part in making a difference."

Then, it became apparent some elected officials had "political priorities" that conflicted with their goals for gun reform and school safety, he said.

"The frustration sets in as you try to help your child make sense of it all and decide the next course of action."

He said one way Students for Change moved forward was by organizing a gun violence summit that brought together people from across the country to discuss policy solutions.

It's one way members of the Parkland community are working to honor the memories of those who died one year ago.

"Every day has been a day that we've thought about it here in Parkland. We hope the rest of the country can step up."