Updated throughout at 7:15 p.m. on April 20

Thousands of students across North Texas and the nation walked out of schools on Friday, saying they shouldn't fear for their lives while in class.

On the 19th anniversary of the Columbine massacre in Colorado, many students set aside their fear of now-common school shootings to raise their voices against what they see as political inaction on meaningful gun control.

Some faced pushback. That included armed men in Frisco and threats against a high school in Keller.

The National School Walkout day was the latest in a series of student-led protests following the shootings at Marjory Stoneman Douglas High School in Parkland, Fla., that left 17 people dead in February. More than 2,500 high schools were expected to participate across the country, with at least one protest in each of the 50 states.

Students chose the Columbine anniversary for the walkouts to honor the 12 students and one teacher who were gunned down at the suburban school 30 miles from downtown Denver.

At Heritage High School in Frisco, students learned a lesson about Texas gun laws during Friday's school walkout.

After students had gathered in the school's gym for a rally, a few headed toward a nearby park to continue their protest beyond the 30 minutes allotted by the school district.

That's when a few men were spotted carrying long guns slung across their shoulders just off campus. Student organizers said in a tweet that the men were protesting the walkout "and did not appear to be planning anything" and were more than 500 feet from the campus.

"We didn't know people could just legally carry AR-15s in the street," said junior Kundai Nyamandi, 16. "That was really jarring for most of us."

1 / 6Students from Frisco ISD's Lone Star High School students left the school during the National School Walkout on Friday morning.(Ron Baselice / Staff Photographer) 2 / 6Students walkout of MacArthur High School in Irving to protest gun violence, Friday, April 20, 2018.(Brandon Wade / Special Contributor) 3 / 6Students at Frisco ISD Lone Star High School participate in the National School Walkout Friday morning April 20, 2018.(Ron Baselice / Staff Photographer) 4 / 6Lone Star High School students listen to fellow student Evan Branco, 18, right, during the National School Walkout in Frisco, Texas Friday morning, April 20, 2018.(Ron Baselice / Staff Photographer) 5 / 6Frisco ISD 's Lone Star High School students signed a petition demanding change in gum laws.(Ron Baselice / Staff Photographer) 6 / 6Frisco ISD Lone Star High School student, Hillary Shah, 17, leads the moment of silence in the National School Walkout in Frisco, Texas.(Ron Baselice / Staff Photographer)

Kundai couldn't see their guns, but she and other students decided to head in the opposite direction to a different park.

As one of the walkout's organizers, Heritage senior Ryan Short said he felt responsible for the safety of every student who decided to take a stand.

"I was freaking out," he said when he saw the armed men from a distance. "They did that with the sole purpose of intimidating students, most of whom are minors."

The men didn't interfere with the students' peaceful protest, and they eventually left without incident. But they spurred a healthy discussion that continued through the afternoon.

Frisco police said the men weren't violating Texas law, which allows the open carrying of long guns

But at Keller High School, a pep rally and a planned walkout were canceled by organizers and school administrators after Keller ISD received a threat of violence. Security was stepped up.

In Ocala, Fla., a 17-year-old was shot and wounded at Forest High School. Police later took a 19-year-old into custody. The shooting took place less than two hours before that school's walkout was to take place.

The Dallas Morning News sent reporters to a handful of the North Texas protests. Here's a closer look at a few schools:

Lone Star High School in Frisco ISD

More than 260 students met at a field behind the campus of Lone Star High School in Frisco, carrying signs, chanting against the National Rifle Association and circulating a petition with dozens of signatures demanding change.

Senior Hillary Shah said she had seen the faces of too many school shooting victims on the news. "That could have been any of us," she said.

The nation's students sent a clear message during Friday's walkout, she said: "Enough is enough."

Petition signed by dozens of the more than 260 students at Lone Star HS in Frisco who walked out of class against gun violence today. @fisd_walkout pic.twitter.com/HaK0dO6Kw0 — Valerie Wigglesworth (@vlwigg) April 20, 2018

Shah had spent long hours over the past month meeting with students across Frisco ISD to plan a peaceful event that she hopes one day will lead to changes at the national level. Her efforts paid off with a shoe box full of letters from the Lone Star walkout that she will be sending to Congress.

Senior Mariana Herreria is not only old enough to vote but also savvy enough to recognize its importance. She trained through the Denton County elections office to become a volunteer deputy registrar. That allowed her to collect voter registration forms from students during the walkout.

She said she decided to get involved because adults weren't doing enough.

"We are the generation of change," Mariana said.

Lone Star High School senior Hillary Shah on tower addresses more than 260 students who walked out of class today against gun violence. Too many school shootings, she said. "I stand out here and say never again." @fisd_walkout pic.twitter.com/mi47sHLNQs — Valerie Wigglesworth (@vlwigg) April 20, 2018

Lone Star HS students hold moment of silence for 47 seconds to represent the 47 kids on average who are killed every day by gun violence @fisd_walkout pic.twitter.com/8nbrveID2S — Frisco, TX News (@Frisco_news) April 20, 2018

Petition signed by dozens of the more than 260 students at Lone Star HS in Frisco who walked out of class against gun violence today. @fisd_walkout pic.twitter.com/HaK0dO6Kw0 — Valerie Wigglesworth (@vlwigg) April 20, 2018

Lone Star HS sophomore Ynigo Villanveva walks out of school in Frisco as part of National School Walkout against gun violence @fisd_walkout pic.twitter.com/CmJ68U4ew3 — Valerie Wigglesworth (@vlwigg) April 20, 2018

Lone Star High School senior Blair Finlinson performs during National School Walkout against gun violence today in Frisco @fisd_walkout pic.twitter.com/9UbdXZ1xAr — Valerie Wigglesworth (@vlwigg) April 20, 2018

Arlington High School

About 40 students gathered at the football field tucked away behind Arlington High School.

That wasn't good enough for a handful of teens, who carried their signs along busy Cooper Street to City Hall about a mile away. They knew they might get in trouble for leaving campus but said the need for tighter gun control was more important.

"We can't keep this to ourselves back there. ... We are marching all the way to City Hall to make sure our voices are heard," said Alyasia Johnson, a junior.

A handful of teens holding signs along busy street in Arlington wanting a stop to #GunViolence #NationalSchoolWalkout #TxEd pic.twitter.com/IKH7Gr1DQ6 — Eva-Marie Ayala (@EvaMarieAyala) April 20, 2018

Classmate Jeweliana Johnson, a sophomore, said kids need to learn in a safe environment. She said her uncle was at a club when a drive-by occurred and a young cousin was at a party when a fight broke out. Both were killed, she said.

And then there was that scary moment last month when police swept her school after reports of a suspicious person near campus.

“We've had school lockdowns with police at our school before,” she said. "I've lost family to gun violence and nothing has changed. Something has to change."

Jasper High School in Plano

Nearly 100 students gathered outside Jasper High School in Plano, giving 17 speeches — a nod to each individual who died in Florida during the Valentine's Day shooting.

The students shared contact information for a congressman so students could call and write him to urge stricter gun control.

"We need actual change," sophomore Medha Anoo told the cheering crowd.

1 / 3Students gathered outside Plano ISD's Jasper High School in Plano for the National School Walkout.(Ron Baselice / Staff Photographer) 2 / 3Parents watch their daughter participate in Plano ISD's Jasper High School's National School Walkout in Plano, Texas Friday , April 20, 2018. Jasper students gathered on school grounds early afteroon, the walkout is in conjunction with the 19th anniversary of the Columbine shooting and other school shootings.(Ron Baselice/The Dallas Morning News)(Ron Baselice / Staff Photographer) 3 / 3Students at Plano ISD's Jasper High School gather on school grounds for the National School Walkout in Plano, Texas Friday, April 20, 2018. The walkout is in conjunction with the 19th anniversary of the Columbine shooting and other school shootings. (Ron Baselice/The Dallas Morning News)(Ron Baselice / Staff Photographer)

About 100 yards away on a public sidewalk, her mother and other parents strained to hear. One father who tried to get closer to take photos was asked to move off school property.

The father said his daughter Katia had nightmares about school violence following the February shooting. So she decided to fight back, even making him drive her to last month's March for Our Lives rally at Dallas City Hall.

Later, Katia said she'd been inspired by Emma Gonzalez, a survivor of the Stoneman Douglas shootings. Emma has become an activist calling for gun control.

Katia said she was surprised that so many classmates gave up their free time to participate.

"There was no slandering of any political party — just us simply saying, 'We want gun regulation,'" she said.

A woman walking dogs alongside the Jasper campus asked why the teens were gathered. When she learned why, she turned toward the kids and said, "Oh for God's sake. The Second Amendment!"

The parents smiled at her politely as she walked away. One mother looked at the kids, then back toward the woman. "These kids are showing us an example of how to use our voices," she told the other parents.

Irving MacArthur High School

Junior Kealie Jordan organized the walkout at MacArthur High School in Irving only a week ago, unsure whether anyone would participate. She was surprised when about 150 classmates joined her.

"I didn't know that this has touched so many more people's hearts," she said.

Asked why they were protesting, several students brought up safety, both at school and in the larger community.

"I'm tired of us being scared to go to class and stuff," freshman Janae Durham said. "We shouldn't have to live like that."

At MacArthur High in Irving, sophomore Damien Miles held a sign reading, "How much tears and blood will it taker?!" (Brandon Wade / Special Contributor)

Kealie spent a good deal of her time in the first hour of the protest wrangling wayward students, keeping them off the school's driveway and trying to draw back some who were sneaking off for lunch.

"I have to make sure that I lead a peaceful protest where everyone's knowledgeable about what we're out here for — not to just walk out of school," she said.

Her message to adults: "Don't underestimate the youth. Because we are becoming knowledgeable, and we aren't taking a traditional stance — conservative or liberal. ... It's not about political sides. It's about the future of America."

Junior Kealie Jordan (right) led her classmates in a sometimes emotional walkout at MacArthur High School in Irving. (Brandon Wade / Special Contributor)

19 years after Columbine, students still at risk of school shootings. “We need actual change,” said Medha, a Jasper HS student in Plano #NationalSchoolWalkout — Eva-Marie Ayala (@EvaMarieAyala) April 20, 2018

“For God’s sake. The second amendment!” A woman walking dogs past Jasper HS said #NationalSchoolWalkout #txed — Eva-Marie Ayala (@EvaMarieAyala) April 20, 2018