What happened at Columbine High School 25 years ago wasn’t the first or the last mass shooting at a school in America, but it was the first covered in a 24-hour news cycle and it remains deeply ingrained in the American psyche.

The tragedy prompted a national debate on guns and mental health and unprecedented changes to school security.

“I loved Columbine,” Frank DeAngelis, the former principal of Columbine High School said. “It was like my second family. And then April 20, 1999 came, a day in which my life changed forever. And not only my life. I think it changed the country and the world.”

Seconds matter: How Columbine changed police response

DeAngelis retired in 2014 from Jefferson County Public Schools after 30 years, 18 as principal at Columbine, including that fateful day. He now helps others work through the trauma similar to what he experienced at Columbine.

On April 20, two students killed 12 schoolmates and a teacher and injured 21 others before taking their own lives. The tragedy shattered the belief that children were safe at school and upended the way law enforcement responds to active shooters.

“It was a pivotal moment on how law enforcement responds to these things,” said Denver Public Schools Chief of Safety Greg Cazzell.

“We no longer wait,” Cazzell added. “That started changing the response.”

Columbine students give back during 25th anniversary of shooting

‘The worst thing that we can do is not be prepared’

Before Columbine, there wasn’t a standard response for active shooter situations.

“The only drills we did back in 1999 were fire drills,” DeAngelis said.

In the wake of the shooting, law enforcement’s response underwent significant changes. Gone were the days of negotiating with the shooter or waiting for a SWAT team to respond. School districts and law enforcement agency across the nation began developing active-shooter protocols that emphasized an aggressive and swift response to neutralize the threat.

But as the shootings in Parkland and Uvalde have shown, the response by officers don’t always follow what the protocols outlined.

Columbine 25 years later: FASTER Colorado arms school staff to protect students

In 2018, Scot Peterson, a former school resource officer, stayed outside while Nikolas Cruz killed 17 staff and students at Marjory Stoneman Douglas High School in Parkland, Florida. A jury acquitted Peterson last year, effectively absolving him of any wrongdoing.

And two years ago in Uvalde, Texas police officers waited more than an hour before breaching a classroom as Salvador Ramos, a former Robb Elementary School student, gunned down 19 kids and two teachers.

“That goes against what we learned, at Columbine,” Cazzell said.

Jeffco Chief of Schools David Weiss and Cazzell — as undoubtedly school officials across the nation do — scour the reports that follow a shooting to glean what they can from the missteps.

“None of us want a tragic event to happen, but the worst thing that we can do is not be prepared,” Weiss said.

Part of being prepared — Weiss and Cazzell argued — is bringing the lessons learned from other shootings back to the team.

“Each of the incidents I think we learn from and try to do better,” Weiss said.

‘It’s hard to say if we’re safer now’

There have been 404 school shootings between Columbine and April 2024, according to the Washington Post, which said it pieced together data from news articles, reports from law enforcement, open-source databases and calls to schools and police departments. Some of those shootings did not involve injury. The federal government does not keep numbers on school shootings.

The frequency of school shootings nationally appear to be increasing, according to the Washington Post’s database.

“It’s hard to say if we’re safer now than we were before,” said Rob Gould, president of the Denver Classroom Teachers Association (DCTA). “I’d probably say no.”

The teachers’ union represents nearly 4,000 educators throughout Denver Public Schools or roughly about 70% of the district’s teachers.

Columbine, 25 years later: Complete coverage from The Denver Gazette

School resource officers, or SROs, have long been touted as one of the answers to increased security concerns on campus.

But SROs didn’t emerge in response to Columbine. The practice started in the 1950s. Some maintained it was meant to improve the relationship between local police officers and the youth, while others assigned more explicit racial underpinnings.

In any case, SRO programs gained popularity in the aftermath of school shootings in the 1990s, specifically in Columbine and Jonesboro, Arkansas.

And their presence has grown exponentially since, paid for, in part, with federal funding allocated in respond to school shootings.

In 2020, the U.S. had roughly 23,400 sworn officers in schools across the nation, according to the U.S. Department of Justice.

Denver Public Schools was among a string of school districts across the nation that removed SROs from campuses following the killing of George Floyd by a Minneapolis police officer four years ago and the national protests that ensued.

Then last year, a student at East High School shot two administrators, and, under pressure to respond, the DPS school board reversed its 2020 decision and voted to return SROs to Denver schools.

School resource officers are sworn peace officers who work in a school setting.

Colorado has roughly 300 SROs for its 1,900 school buildings.

While parents in Denver clamored for more police presence in the aftermath of the shooting at the district’s flagship school, teachers largely believed other strategies could be more effective.

What would make teachers feel safer — a DCTA survey last year said — were not necessarily metal detectors, cameras and SROs. Instead, the educators “expressed overwhelming support for smaller class sizes and caseloads and a full complement of student mental health supports to feel safe in schools,” the survey said.

Smaller class sizes means teachers have more time getting to know their students better and their personal struggles to address needs and close learning gaps, the survey suggested.

“That’s about being able to check in with all of your students,” Gould said.

Cazzell agreed.

“It comes down to our students, knowing when they’re in crisis,” Cazzell said.

‘I was terrified’

Brooklyn Madden vividly recalls her first lockdown two years ago and her wide-eyed students who wondered if it was a drill.

Following protocols, she shut out the lights, locked the door and corralled 30 fourth-graders and then steeled herself to assume a role Madden, then a first-year teacher, hoped she would never have to play: protector.

“I was terrified,” said Madden, noting how the weight of that responsibility became real in that moment.

“I was thinking, ‘I don’t know what I signed myself up for.’”

Madden teaches at Mountain Phoenix Community School in Wheat Ridge.

While the school lockdown that day turned out to be a false alarm, Madden knew what to do because of the active shooter training that wasn’t available two decades ago.

The active shooter drills, though, may have its own cost, some said.

Lorie Fernald harbors fear all the time about shooters. She hopes she will remember her training. She worries whether she can run fast enough to lock the door and whether she will be brave enough.

Fernald, who is now a substitute teacher in Lakewood, began teaching a decade before the Columbine shooting. She never dreamed becoming a teacher would require she learn lockdown drills. When she started in the classroom in 1988, the only drills teachers conducted at the time were fire drills.

“I expected to have to keep kids safe like teachers do,” Fernald said.

But not from shootings.

“You know, ‘Don’t run with scissors, Don’t jump off the top of the slide,’” she said. “I never thought about somebody coming in and shooting kids. Never, ever. That never crossed my mind as something that could happen in a classroom.”

Fernald also worries about the long-term impact will have on her students, who often chant during recess after a lockdown drill.

“Locks, lights, out of sight,” they’d say while they play.

“I had a student once tell me: ‘I don’t think about if there’s going to be a lockdown and if there’s going to be an active shooter. I think about when it’s going to happen,’” Fernald said.

“I think we’re underestimating the negative impact this kind of environment has on our students.”

Columbine, 25 years later: Complete coverage from The Denver Gazette

School leaders and those in law enforcement insist there is no silver bullet to America’s gun violence.

That’s why, they said, the safest campuses employ a variety of security layers to get ahead of the threat, including badges and locked doors, secure vestibules that provide administrators control over who can enter, security cameras, SROs and Safe2Tell Colorado, an anonymous way for students and staff to report safety concerns.

“There’s just not one thing that’s going to stop it,” said DeAngelis, the retired Columbine High School principal.

Denver Gazette reporter Sage Kelley contributed to this report.