Twenty-five years ago, Michelle DiManna sat in the math office at Columbine High School grading papers and talking to a colleague when she heard students screaming in terror.

Two heavily armed shooters had entered the Jefferson County school late in the morning on April 20, 1999, and proceeded to kill 12 of their classmates and a teacher, injuring dozens more in a tragedy that shocked Colorado and the nation.

The shooting, which ended with the two killers taking their own lives, reshaped school security across the United States and served as a precursor to the litany of mass killings that have taken place across the country in the decades since — so much so that the school’s very name, Columbine, remains synonymous with school shootings.

But what happened next, after DiManna fled the building with her colleagues and pupils, is also part of Columbine’s legacy, the one that, 25 years later, both current and former employees talk about the most: the resiliency and hope that persists in a community marked by one of the deadliest school shootings in American history.

“We take care of each other,”  DiManna, who still teaches math at the high school, said in a recent interview. “You don’t really leave your family after trauma — and that is what Columbine is.”

And that’s why the 53-year-old, who will retire at the end of this academic year, has spent her entire career at Columbine despite such tragedy. DiManna is one of 15 current Columbine staff members who were either employees or students at the time of the shooting.

As Jeffco Public Schools marked the shooting’s 25th anniversary, officials held a media day with Columbine and district staff earlier this month to talk about the changes to school security that occurred nationwide in the wake of the shooting, such as lockdown drills and the creation of Safe2Tell, Colorado statewide anonymous reporting system for students.

Much has changed in 25 years. Those who were students at the time of the shooting have become parents and the pupils that now sit in the high school’s classrooms are too young to remember the tragedy, having not been born until years later.

One thing that hasn’t changed, though, is that at 11:20 a.m. each April 20 — around the time the shooting began — former Principal Frank DeAngelis gathers at the school with families and staff to read the names of the 12 students and one teacher who died that day: Cassie Bernall, Steven Robert Curnow, Corey DePooter, Kelly Fleming, Matt Kechter, Daniel Mauser, Danny Rohrbough, Dave Sanders, Rachel Scott, Isaiah Shoels, John Tomlin, Lauren Townsend and Kyle Velasquez.

“Columbine represents a time to remember,” said DeAngelis, who served as principal for almost two decades, and made it his mission to rebuild the school after the shooting and to help his students through the trauma.

DeAngelis retired in 2014, two years after he fulfilled a promise he made after the attack to remain as principal until all of the students in Columbine feeder schools at the time of the shooting had graduated.

“Columbine also represents hope,” he said. “Columbine is strong.”

The day has also become an annual day of service where students and staff give back to the community through volunteer projects.

“The community came together and made it stronger,” said current Principal Scott Christy, adding, “I hope Columbine is a place of hope for those who have experienced tragedy.”

On the day of the shooting, DiManna was a 28-year-old in her fifth year of teaching at Columbine, a school she also graduated from in 1989.

For DiManna, the moments after she heard screaming followed like this: A teacher pulled a fire alarm to evacuate the building. Her sister, Kim, who was a senior, found her and DiManna told her to leave — but she did not do so herself until after helping evacuate the math department’s classrooms.

DiManna found her sister again outside, where they saw an injured student near a stoplight before going into a house across the street, which is where she called her husband.

Residents opening their doors to students and staff fleeing the shooting isn’t the only thing DiManna remembers. She also recalls youth ministries helping care for students in the days that followed no matter whether they were members of their churches or not.

“I don’t know how many communities could take care of kids as ours did,” she said.

At the time, the shooting at Columbine was the deadliest at a K-12 school in U.S. history. There hadn’t yet been massacres at schools in Newtown, Connecticut, Parkland, Florida, or Uvalde, Texas.

In other words, there weren’t many people who knew what the survivors of the school shooting experienced and how it would affect them in the years that followed. They couldn’t understand how, for Columbine survivors, routine fire drills can be a trigger, how lockdown drills can create a panic, or how each year when April rolls around, so, too, comes anxiety about what might happen, DiManna said.

That’s also why DiManna stayed at Columbine. The support that the community provides didn’t end 25 years ago, she said.

Christy, the school’s principal, checks on the staff members who were at Columbine in 1999 each time there’s another school shooting or something else happens that could upset them, DiManna said.

“We just pick each other up,” she said. “You always knew if you were having one of those days, or something happened, you had someone to talk to.”

The reason DiManna returned to Columbine after the shooting is also simple.

“I wanted to teach,” she said.

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