Helena Moreno, center, joined a protest against guns Saturday on the steps of the Broward County Federal courthouse in Fort Lauderdale, Fla. (Brynn Anderson/AP)

The boldest voices to emerge in the wake of last week’s mass shooting at Marjory Stoneman Douglas High School in Parkland, Fla., have been unexpected ones. Surviving students at the school quickly spoke out on social media and to news cameras about the violence and, more broadly, about political leadership that they saw as having let them down.

In the days since, those voices have grown even louder: pointed speeches, essays in the New York Times, interviews on national news networks.  There have been excoriations of elected officials — especially President Trump and Sen. Marco Rubio (R-Fla.) — on social media. And the students are raising money for a national march they’ve planned for next month.

This isn’t the type of action we’ve seen after past shooting incidents. But there are a number of reasons, despite the uniqueness of seeing student victims speak out, we shouldn’t be surprised that after this shooting — in this place at this time — we’re seeing young people mobilizing and making themselves heard.

They are a post-Columbine generation

The mass murder at Columbine High School in 1999 was one of the first in a new pattern of school shootings: It was premeditated, with the goal of killing as many people as possible. For those of us who were already adults when that occurred, it was shocking both because of its devastation and because of how aberrant it seemed. Since then, we’ve seen several other mass shootings that followed a similar pattern, at Virginia Tech in 2007, at an elementary school in Newtown, Conn., in 2012 and now in Parkland.

These were all shocking events. For the students in Parkland, though, they weren’t as shocking as they were to those who knew a world before these killings were common. For us, these were horrific aberrations carried out by individuals. For them, for a generation that grew up preparing for mass shootings the way those who are older grew up with fire drills, this shooting is part of an endemic problem that’s been with them their whole lives.

We see these mass killings as a series of tragic one-off incidents, which can make them seem harder to prevent. They are more likely to see school shootings as entrenched, and therefore better able to be understood and prevented.

They are old enough to speak out

Those born after Columbine are just entering adulthood. The survivors of the massacre in Newtown were still children. The survivors in Virginia Tech largely grew up pre-Columbine. This is the first premeditated mass shooting at this scale that involved people who both grew up entirely in a world in which mass shootings were common and which targeted people old enough to have a voice.

They are at an age at which political awareness blooms

Not only are they old enough to be heard, those in their late teens are also at an age when politics surges in importance.

Voter turnout increases as people get older, a function of greater personal stability (moving less often), and that voting tends to be habitual. But there’s evidence that those who are newly able to vote do so much more heavily than people even slightly older, in part a function of the novelty of being able to do so.

More broadly, the events experienced when you’re 18 are three times as powerful as events experienced at age 40 in terms of forming political views, according to analysis conducted by Catalist in 2014. The ages from 14 to 24 were found to be the most formative years.

Young people are also more likely to be politically liberal, although they’re only slightly more likely to be supportive of gun-control measures.

They’re not cynical

At ProPublica, Alec MacGillis writes that pessimism among liberals after years of seeing no significant changes to the nation’s gun laws can be self-fulfilling.

“This world-weary defeatism is self-fulfilling in its own way,” he writes, “and helps explain why Washington hasn’t taken action to address the killing.” Those pushing for change are dismissed as quixotic, he argues, and those who oppose new laws aren’t forced to defend their positions.

The teens in Parkland haven’t been part of the political discussion and don’t show that same defeatism. They’re old enough to have seen how little has been done to address school shootings but not yet old enough to see change as impossible. In the wake of the massacre, they made this point plainly on social media and in interviews: Something can be done, and yet you haven’t done it. It was not a complaint about intractability; it was a complaint about inaction.

They live in a world in which the voice of the individual is powerful

If you are 18, Twitter has been in existence for two-thirds of your life. Facebook, about the same. They’ve seen any number of tweets or Facebook posts go viral; they understand that one person’s voice can be lifted up until it’s heard by millions.

The most retweeted Twitter message in history isn’t Barack Obama’s reelection message or Ellen DeGeneres’s Oscar photo. It’s a teenager who was trying to get free food at Wendy’s.

Young people are less likely to own guns

There’s a correlation between views on guns and gun ownership. Gun owners are more likely to oppose new limits on gun ownership and less likely to see new gun measures as effective.

But younger Americans are less likely to be gun owners, according to data presented by New York University’s Patrick Egan.

That’s not only because they’re younger. They are also less likely to own guns at their current age than were previous generations.

It’s a moment when political disruption seems more possible than ever

Many of the factors above combine with another that’s hard to dismiss. The election of Donald Trump and shifting political power internationally reflect a political moment in which it seems like the old rules don’t apply. This is a function of informal organizing over the Internet and the diminishment of traditional media as conduits for rhetoric, among other things. But it means that the Parkland students are taking political action just as political walls are cracking.

One of the old rules was that the gun-control debate was intractable. Another was that teenagers didn’t have much to contribute to the national political conversation. The past week has made both of those rules seem shaky.

There’s one other factor very specific to the moment:

They have a president who watches cable news

Often, accessing the president means sending a letter and keeping your fingers crossed. The Parkland survivors, though, were able to speak directly to Trump simply by speaking into news cameras.

Trump saw them on television and heard their words. And, as The Washington Post reported Sunday, the students’ advocacy may have helped to influence him.

This article was corrected to fix the date of the attack at Virginia Tech.