EDITOR’S NOTE:  This article contains descriptions of mass shootings that some readers may find disturbing.

The nightmares are visceral — Molly Canty is hiding in a classroom, the gunshots are getting closer and closer, and she can’t lock the door.

It’s not the first time the 21-year-old rising college senior has been traumatized by a mass shooting in a school environment, a uniquely American phenomenon. It’s a nightmare that has been stalking Canty since she was an elementary school student, later again as a middle schooler and now, as a survivor of the Florida State University shooting.

“Everyone just started running,” she recalled to CNN, detailing how a game of Jenga during an outdoor class turned into a terrifying ordeal in April. “There was a lot of mass hysteria, with not really knowing where to go.”

Canty’s series of tragic experiences seems extraordinary, but it’s a testament to the reality of so many children today; the trauma of gun violence is becoming harder and harder to escape. Gun violence has been the leading cause of death for youth in America since 2020.

Her life experience to this point had made her hypersensitive to the danger of gun violence in schools. Despite that, she says she was one of the slowest to react as gunshots started just 100 yards away. She can vividly recall her professor running barefoot, one of her classmates scrambling in only her socks, the two old men walking slowly, who she turned to and screamed, “Active shooter! Run!”

The series of sounds that came next would punctuate her memory. She heard 15 to 20 gunshots, then sirens and helicopters. When she managed to get to a safe place, a sound-proof podcasting studio, she said she couldn’t breathe.

When she was 8 years old, Canty remembers hearing a blood-curdling scream and seeing a teacher running down the hall at school. She was startled and confused.

A nervous tension had been building at Hart Magnet Elementary School in Stamford, Connecticut, since earlier in the day. She vividly remembers her third-grade teacher calmly standing up with a strange look on her face and locking the door. They ate lunch in their classroom that day, which was unusual.

Only later would she learn the distraught teacher’s best friend had been gunned down at the Sandy Hook school about 40 miles away, and the innocence of their childhoods had been torn apart, too, she said.

Canty remembers her mother had a quiet demeanor when she picked her up from school that day.

“One of my mom’s friends came over with her daughter and … turned on the TV in our basement, and that’s when we saw what happened,” she told CNN. “And I remember I still just didn’t quite grasp it.”

Her mother had to explain that a person with a gun went into the school and started shooting children, Canty said. In what remains the deadliest mass shooting at a US K-12 school, 20 students aged 6 and 7 years old, and six staff members, had been slaughtered in their classrooms.

When Canty went back to school, her class spent the whole day making paper snowflakes to help decorate another school where the surviving Sandy Hook children would be relocated. She and her mom made a poster with 26 angels on it and everyone in her class signed it before it was taken to Newtown.

New safety measures went into place in Canty’s school. One of her teachers brought a cord ladder to school, just in case they’d ever need to evacuate from a fourth-floor window, and the classroom doors were locked at all times, Canty said. Parents and older children weren’t allowed in anymore. Then the shooting drills began, and so did the trauma.

Active shooter drills at K-12 schools may do more harm than good, according to a 2024 report from Everytown for Gun Safety. They are associated with a 39% increase in depression, 42% increase in stress and anxiety and 23% increase in physiological health problems.

“I was never anxious to go to school, until we heard about Sandy Hook,” Canty explained, but she said that changed within a few weeks. “I had my first big panic attack. My mom had dropped me up to the class and I just immediately started crying. I ran after her. … I was, like, ‘I can’t stay in the room.’”

Canty said she began experiencing almost daily panic attacks and no matter what she did, she was “anxious about everything.”

“I was just so terrified that someone was going to come into my school, do that and try to hurt my friends,” she said. Knowing her brother would soon be a kindergartner only heightened her anxiety.

Anne-Marie Canty remembers the night terrors that plagued her daughter after Sandy Hook — the sleep disorder torments individuals who appear to be awake, although they are not fully conscious.

“She would just start screaming, and I would come in and she would be sound asleep,” she said. “As a parent, you’re going, ‘Oh my gosh, what are we doing to our kids here?’”

Sometimes Canty would wake up from the nightmares and throw up, her mom said, adding she would often sleep the night in her parents’ bed until she was 10 or 11. “She lost an awful lot of weight. … It had a big, profound impact on her.”

Experts who have been studying trauma in children know they don’t have to personally experience a shooting to be affected by one. When a child hears of an event that challenges the notion of safety in a school, it makes them question all the other assumptions they have about the world, Dr. David Schonfeld, the director of the National Center for School Crisis and Bereavement, said.

Molly had been profoundly affected by the Sandy Hook shooting, which made her more anxious and less trusting. At age 8, she was beginning to understand she might have to be responsible for her own safety at school.

Knowing how to find the exits wasn’t enough to calm Canty’s nerves when she was 11. She was at her middle school when the fire alarm blared and nobody could get out – it was a day after the 2018 Parkland, Florida, shooting.

Canty said she knew the Parkland shooter had lured students into the halls by pulling the fire alarm, something that flashed through her mind now.

“I remember being really scared after that,” she said. “All of the doors around us were heavy metal doors and they just locked, and I was stuck in a circle with probably 50 other kids, and we couldn’t go anywhere.”

Canty said she always had an exit strategy and not having a way out of the room panicked her. Luckily, there was no threat, but the school lockdown rattled her, especially less than 24 hours after 17 people died at Marjory Stoneman Douglas High School, the worst high school shooting in America.

While riding the school bus home that day, Canty learned a girl she knew, 14-year-old Cara Loughran, was killed in the Parkland massacre.

Loughran and Canty were both part of the Drake School of Irish Dance, which has studios in Georgia, Alabama, South Carolina and Florida. Canty recalls having a conversation with her and seeing her at workshops and dance competitions.

In the aftermath of the Parkland shooting, students at the dance school wore purple ribbons in remembrance of Cara. “We would always honor Cara and … tried to focus on dance, because she couldn’t.”

For some survivors of Parkland who attended the dance school, the clickety-clack sound of the hard shoes triggered flashbacks of the gunfire, and some had to take a break from dancing and be comforted by therapy dogs, the studio said.

By the time Canty was in high school a few years later, she said the fear of an attack at her own school was never far away, recalling being frightened by seeing National Rifle Association stickers when her family moved to the South.

She estimates there were around a dozen threats during her four years there. On one occasion, when she was volunteering at the school’s front desk, a man was spotted with an AR-15-style rifle in the shopping plaza parking lot across the road. The threat turned out to be benign, but the panic of lockdown was real.

“I was really hoping that was going to be my closest experience.”

As Canty sat trembling for three hours in her professor’s podcasting studio at FSU, she was surrounded by friends, classmates and strangers who had been smashed together by the chaotic terror.

“There was just tears running down everyone’s faces, and no one really knew what to say,” she recalled. “The girl that was next to me in the room was a freshman and she wasn’t in our class. … She was just hysterical. I just was holding her hands and hugging her.”

“I didn’t even know some of their names, and it was so weird to see us kind of all breaking down at the same time,” she said.

Canty left the studio when an officer found them and led them to safety. Canty knew him – he was one of the campus police officers who took a celebratory 21st birthday photo with her just two days prior.

She says she was among one of the last groups to have been rescued, and her roommates were waiting at home to greet her. “My legs gave out underneath me. I just felt everything kind of hit at once,” she said. She took some sleeping pills that night, but the nightmares, much like those she endured in elementary school, quickly returned.

A week after the shooting, Canty had barely slept for longer than three hours a night. At times her legs hurt so much she could hardly walk. She was numb and tired, and her primary emotion was anger.

“The rage I felt towards (the shooter) is indescribable,” she said. “I just felt rage and anger for the first couple of days, but then I would break down and start crying and I couldn’t stop.”

The shootings are changing life for the generation experiencing them firsthand, one expert says.

“We are growing a whole population of kids who will eventually be adults with anxiety disorders, post-traumatic stress disorder, and lack of trust and fear in the world around them, all which they wouldn’t have had if it were not for the shootings,” Dr. Gail Saltz, a psychiatrist and clinical associate professor of psychiatry at New York-Presbyterian Hospital and Weill Cornell Medical College said. “Without help, this causes avoidance, avoidance of school, the very thing that they need to be able to truly grow as adults and be successful in life.”

A school shooting should never happen to anyone once, let alone twice, yet a whole generation of children are being forced to repeatedly run for their lives. Some FSU students with connections to Parkland have now experienced two deadly school shootings in seven years.

Before the FSU shooting, Canty already had a psychiatrist, but she made an emergency appointment so she could navigate her new nightmares under medication. She was at a rock concert a couple weeks later and had to step outside to calm herself down, fearing she wouldn’t be able to hear gunshots over the noise of the drums.

Since she was forced to as a child, Canty has learned the only way to tackle her fears is to face them head on.

Counselors at the university urged Canty to try and reestablish a normal routine as quickly as possible, so she and her friends returned to one of their happy places, ironically, the precise scene of the shooting.

She felt her legs buckle again when she saw blood still on the pavement, and it looked as though the grass had been replaced in another spot. Canty and her friends would often hang out and have coffee on the steps outside the Moore Auditorium.

But her anger remains.

“That was always my safe space right there, and that was where he was shooting,” she said. “He came on to our safe space, and tried to take it away, and he took a piece of every FSU student that wasn’t his.”

Canty hasn’t been back to the podcasting room — and she doesn’t want to. The green, however, feels different still.

“I haven’t been able to relate that room to anything other than just being terrified,” she said. “The green where he was shooting… I relate that to just happiness.”

CNN’s Christina Zdanowicz contributed to this report.