How young survivors of mass shootings cope with trauma: 'Everything's changed'

The Uvalde, Texas, community is still reeling two weeks after a gunman opened fire at Robb Elementary School, killing 19 students and two teachers. Those suffering include young survivors who witnessed the horror.

As survivors of past school shootings move forward, the psychological injury that comes with witnessing such events often remains.

Since the 1999 massacre at Columbine High School in Colorado, at least 185 children, teachers and others were murdered and 369 were injured in U.S. school shootings, according to a Washington Post database.

And over the past two decades, 311,000 children in more than 330 schools have been exposed to gun violence during school hours, according to the database.

WATCH: Uvalde teacher describes moment he saw shooter, trying to protect students

Fourth-grade teacher Arnulfo Reyes was wounded but survived the shooting at Robb Elementary School in Uvalde. He shared his story with ABC News.

Last year, there were 42 acts of campus gun violence at K-12 schools in the U.S., according to the gun violence prevention organization Sandy Hook Promise and the Center for Homeland Defense and Security.

Yet the mental wounds from school shootings rippled out far beyond the hospital beds.

"They are holding onto this terrible, horrific memory," said Dr. Amanda Wetegrove-Romine, a San Antonio psychologist who attended high school in Uvalde and assisted in community counseling services in the days after the Uvalde shooting.

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There was blood in the hallway and children were covered in it, a student who survived the elementary school shooting in Uvalde, Texas, told ABC News.

Children were having nightmares and clinging to their parents, she said.

One third-grader, 8-year-old Jeremiah Lennon, feared he would be killed if he went back to school after surviving the shooting in a classroom next to the room where three of his friends were slain. He was changed by the shooting, his grandmother Brenda Morales said, now sitting quietly, not eating much and just staring into space.

"He's changed. Everything's changed," she said.

Aalayah Eastmond was 16 years old when gunshots filled the halls of her high school -- Marjory Stoneman Douglas in Parkland, Florida - in the 2018 attack that left 14 students and three staff members dead. In the years since, she said learns about a new school shooting seemingly "every single day."

"We were the third classroom shot into from the perpetrator. Six of my classmates were shot, and two died in my class," Eastmond said.

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Mia Tretta was also a teenager, just 15 years old, when a gunman charged Saugus High School in Santa Clarita, California, and shot her. Two classmates were killed, including her best friend, who died next to her during the attack.

"Every time I see another shooting happen, it just brings it all back," she said.

Both Eastmond and Tretta said their experiences changed their lives forever.

"Every time you walk into a crowded area, you'll still feel it," Tretta said. "You can still do your best to get a little better, even if it's just a tiny bit each day."

Mental health experts said that because most of the victims were children, trauma can have a particularly long-lasting impact.

"They are in an important stage of development. Their worldview is forming and they are learning whether the world is safe or unsafe," said Dr. Arash Javanbakht, who directs the Stress, Trauma, and Anxiety Research Clinic at Wayne State University.

"Trauma stays with children the rest of their lives," he said, adding that childhood trauma has been linked to a host of health problems later in life.

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Funerals began Monday for some of the victims in the Uvalde, Texas school massacre. They'll be taking place almost every single day for the next two and a half weeks.

Survivors of Columbine, now adults, spoke out in recent days to say news of the shooting reopened the wounds of their trauma.

Mental health experts said a range of support will be needed for the survivors, beginning with what is known as "psychological first aid" in the immediate aftermath to counseling sessions to address trauma symptoms that can last for months and even years. The ability of the community to come together to heal will also be crucial, with parents playing an important role in discussing emotions with their children.

"Support and connectedness with community members and fellow survivors can be a powerful source of resilience, collective remembering, collective healing and purpose," said Nicole Nugent, an expert in treatment for post-traumatic stress disorder who works as a professor of psychiatry and human behavior at the Warren Alpert Medical School of Brown University.

The long-term healing process following a school shooting is different for everyone, said Melissa Brymer, a doctor who specializes in childhood traumatic stress and acted as the head advisor to the Newtown Public Schools Recovery Program following the massacre at Sandy Hook Elementary in 2012.

"There are proper trauma treatments that can help kids, both with their trauma reactions and grief reactions," she said. "We also know that these events change kids. We really do want to foster their strengths as we as they go through this journey of healing."

The Associated Press contributed to this report.