Jackson Mittelman and Tommy Murray stood on Saturday’s biggest stage, in Washington, and recalled being in lockdown in sixth grade on Dec. 14, 2012.

That was the day a gunman entered Sandy Hook Elementary School and killed 20 children and six adult staff members with a Bushmaster AR-15 variant, before killing himself.

“It was one of the worst days of my life,” said Murray, whose mother, Po Murray, is the chairwoman of the Newtown Action Alliance. Murray and Mittelman, who are co-chairmen of the Junior Newtown Action Alliance, and their classmates from Newtown High School carried a message of solidarity to D.C. for their counterparts at Marjory Stoneman Douglas High School.

“After Parkland, we feel hope,” Mittelman said, as he and others presented a banner Saturday to students from that Florida town, where grief from a school shooting has galvanized into youth activism. “After the media trucks leave, we will stand by you.”

Along with hundreds of thousands, the students came together in D.C. in a call for action dubbed the March for Our Lives.

The banner read: “Newtown High School stands with Stoneman Douglas,” and featured the image of a red ribbon.

“We hope our message from Newtown High School will help you through your darkest days,” Mittelman said to the Parkland students.

Student survivors of the Feb. 14 mass shooting that took 17 lives at the Florida high school were the primary speakers and motivators at the D.C. rally, one of hundreds that took place across the nation Saturday, including events in New York, Chicago, Los Angeles, Boston, Dallas, Atlanta and Parkland.

Rallies took place in numerous cities in Connecticut as well, including Hartford, Stamford and Guilford.

In Hartford, the proximity to Newtown was not lost on those who spoke during a two-hour rally or the crowds that marched to the Capitol building’s steps.

New Milford High School senior Shealyn Baumgarner, who marched with junior Thomas King, said her school’s closeness to Sandy Hook was one of the reasons she was spurred to action after Parkland.

“Being one town over from Newtown, it hits really hard,” Baumgarner said.

As they marched, King held a sign that read, “We march because they can’t,” with an arrow pointing to Baumgarner’s sign, which had a long list of the names of those lost in recent mass shootings.

The students said they have been disturbed by incidents at their own high school. Earlier this month, two students were arrested at New Milford High School, one for a small fire set in a bathroom and another for threatening a teacher.

When asked what they hoped would come from the march, King replied simply, “Something, just about anything. Nothing has been done for far too long.”

In D.C., young people from Chicago, Washington, Los Angeles and elsewhere also stepped to the podium, recounting lives in turmoil after acts of gun violence.

“If you listen real close, you can hear the people in power shaking,” said David Hogg, a Stoneman Douglas student. “We’re going to make this a voting issue. We will get rid of these public servants that only serve the gun lobby. And we will save lives.”

Newtowners speak out

The demonstration in Washington appeared likely to draw 500,000 participants — a massive outpouring by D.C. standards.

Sandy Hook was not the nation’s first mass shooting at a school. But it has stuck in the nation’s collective consciousness because the 20 childhood victims were ages 6 and 7. Similarly, the Stoneman Douglas shooting stimulated a movement among teenagers that is widely seen as rejuvenating the push for greater regulation and restriction of guns.

The Newtown group chartered eight buses that left before dawn and arrived in downtown Washington just in time for the noon rally on the Mall, four blocks west of the U.S. Capitol.

Virtually all of the speakers were high school students whose calls for action were punctuated by performances of stars including Ariana Grande, Demi Lovato and Lin-Manuel Miranda.

Inaction by Congress was a common theme, even though the just-passed Omnibus spending bill included Fix NICS, co-authored by Sen. Chris Murphy, D-Conn., and language clarifying authority for the Centers for Disease Control and Prevention to conduct research on gun violence.

“Together, our stories will create the change we need,” Tommy Murray told the cheering crowd, which chanted “never again, never again.”

“If these shootings can happen in Parkland and Newtown, they can happen anywhere,” he said.

Sandy Hook Promise co-founder Nicole Hockley, whose son, Dylan, was killed in the 2012 shooting, reflected on how far the movement for more gun control has come since then.

“I’m just excited that all these people are here,” Hockley said. “We haven’t had a march like this for this issue. It’s good to know so many people are here demanding change.”

Hockley noted a “sea change” in the wake of the Stoneman Douglas High shooting.

“Sandy Hook started this (movement) and it’s been growing ever since, but now the kids are raising their voices,” she said.

Speaking to a crowd of hundreds in Hartford, Erica Lafferty, whose mother, Dawn Lafferty Hochsprung, was Sandy Hook Elementary School’s principal and was killed in the 2012 shooting there, also noted after the Florida shooting, things are different.

Citing the changing weapon-sales policies of retail outlets such as Dick’s Sporting Goods, Lafferty said, “CEOs are changing their policies, and that didn’t happen when I was thrown into this movement five years ago. The tide is changing. The best advice I have for you is to keep going.”

Counter-demonstraters also take stand

The National Rifle Association was mostly silent leading up to Saturday’s rallies. But there were some counter-demonstrators in Washington. A group of people wearing military-style camouflage and calling themselves the Patriot Picket stood about a block from the main demonstration, holding signs that said, among other things, “good guys with guns stand by you.”

“No matter what you want to do, American freedoms are not the enemy,” said Jeff Hulbert, founder of the group based in Annapolis, Md., that brought about 45 people. The group’s website says it mounts protests to counter anti-gun demonstrators. “Looney lefties everywhere,” said a posting on its Facebook page Saturday.

Since the Florida shooting, President Donald Trump and Republicans on Capitol Hill have called for greater focus on mental health and early pinpointing of troubled students. And they coalesced with Democrats around Fix NICS.

But Murphy and other Democrats have insisted tougher restrictions on guns must be part of any effort to reduce gun violence. At a meeting with lawmakers from both parties last month, Trump appeared to embrace much of the Democratic agenda, only to back off after a subsequent meeting with NRA leaders.

Votes for change

Another speaker in Hartford was one of the organizers of that march, University of Bridgeport student Tyler Suarez.

“School safety should not be a political issue,” Suarez said. “There is not a left school or a right school. These are our children, these are our siblings, these are our friends.”

Greenwich High School Roots and Shoots Club President Rene Jameson, 18, was one of the many in Stamford’s Mill River Park.

“I’m so excited to see youth engagement,” Jameson said. “I’m hoping GHS students and Roots and Shoots remember civil disobedience doesn’t need to be convenient.

“We shouldn’t be afraid of the consequences,” she said. “We need to address these issues.”

Jameson said the comment on convenience was a criticism of her high school’s decision to hold a nonpartisan, scheduled rally in the Student Center with speakers from student government earlier this month on the day that students across the nation held walkouts to protest gun violence.

“There’s been a lot of mixed reactions about what GHS did,” she said. “Instead of a walkout, administration got involved. ... It was put in the schedule.

“It’s not supposed to be convenient,” Jameson said. “I appreciate their efforts but it wasn’t enough. We need continued action. We will be doing more.”

In Guilford, state Sen. Ted Kennedy Jr., D-Branford, said as someone who had two uncles killed by gunfire in broad daylight — and whose family has had to relive the tragedies through news clips and the Zapruder film — he was never prouder than Saturday to be a member of the shoreline community, because of the strength of the outpouring on the town green.

Kennedy said last year the NRA gave $38 million to politicians, but Saturday’s show of solidarity on the gun control issue sent a far more powerful message.

“We are going to make a meaningful change,” he said.

Pamela Ruddell, Pam McLoughlin, Jennifer Turiano and Bloomberg News contributed to this report.