A small group of students are crouched on the floor, behind their classroom desks. They are listening to an echo of a gunshot somewhere in their school. It’s quiet for a moment, and someone says “holy s—.” But before the word is finished, the shooting begins again. This time, the bullets are close. It’s hard to tell, but the gunman appears to be firing into their classroom.

The students scream. Eighteen shots. The shooting feels as if it lasts forever. One of the screams stays in your ears, the kind of scream that hurts your throat to make.

You were not there. But a student with a camera was. The video, first uploaded to Snapchat, has been viewed more than a million times just on Twitter in the day since the shooting at Marjory Stoneman Douglas High School in Parkland, Fla. The video was copied, re-shared and broadcast on mainstream news networks before we knew how many people had died at the school, or the name of the alleged gunman. The worst moment of these students’ lives went viral in a matter of minutes, without us knowing whether the teenagers we saw and heard in it had even survived.

We are, at this point, familiar with the experience of watching a mass shooting unfold online. There’s even something of a routine to it: the first reports of a shooting, the growing sense of its seriousness and the onslaught of information, misinformation and rumors that spread. On Wednesday, a school full of terrified teenagers changed that routine: Using their cellphones, they brought us closer.

Tragic events like the Parkland shooting are often defined by images as much as they are words and facts. A photo of a line of small children, walking with their hands on each other’s shoulder as Connecticut police lead them away from their school, is how many remember the 2012 Sandy Hook Elementary School massacre. Others remember watching teenage students running from Columbine High, hands placed on their heads.

In the 2015 Paris attacks, it was a graphic video outside of the Bataclan as concertgoers fled the massacre inside. In the Las Vegas massacre, videos from the concert floor. This school shooting brought us inside a classroom. And not just one classroom. Students were sharing their experience, often in real time, with the rest of the world.

Snapchat published a selection of videos that students, in the middle of an active shooting, uploaded to the platform. They played together as a story.

First, a video of students, parents and teachers, waiting and checking their phones, standing on the side of a road near the school. A police car drives by.

Then, a graphic-content warning. An edited clip of the gunfire video from inside a classroom plays.

Then, we’re transported to another classroom. “What the f— is happening,” a kid says into camera in a whisper. He pans his cellphone camera around — his classmates are huddled in a corner on their phones.

A student, in an auditorium, films the SWAT team clearing the stage with their guns drawn.

Another snaps a still photograph, showing their burgundy shoes against a red carpet. The caption reads, “i’m safe.”

Others appeared to tweet photos from inside the lockdown. “My school is being shot up and I am locked inside. I’m f—ing scared right now,” one tweeted. Another student tweeted a photograph of their feet, their black and white socks embroidered with a red heart, as they sat on the floor of their classroom. They wrote, “So much for Valentine’s Day.”

Another video, with more than 4.5 million views on Twitter, showed the SWAT team arriving in a classroom. The students sit together, as someone who appears to be a teacher stands in front of them, staring at the door.

The SWAT team enters, and someone says “Hands, hands!” Their guns are drawn, bright flashlights point at the students. The students, some still with phones in hands, others visibly shaking, raise their hands into the air. Another instruction: “Put your phones away, put your phones away.” The video abruptly ends.

When mass shootings begin to feel routine, we become trained to notice the patterns. On Wednesday, “thoughts and prayers” trended on Twitter in anticipation of politicians offering them to victims because the phrase has become a meme that repeats every time there is mass violence in America. A few tweets falsely identified Sam Hyde as the gunman, an old hoax that has been around for as long as people have experienced mass shootings on social media. And before the suspected gunman’s name was confirmed, people on Twitter were already claiming to have proof that he was antifa, or a Muslim, or a Democrat, or a Trump supporter.

The videos and images that Marjory Stoneman Douglas High School’s students posted felt like an intervention in this cycle: The routine debates and speculation of a mass shooting online, interrupted by a first-person view of gunfire as students crouched behind their desks.

Because of this, the graphic and vivid videos and photos shared by these students have become everyone’s experience of this massacre. This moment could easily become emblematic of mass violence in the social media age. As that happens, there’s a danger in forgetting that the “raw” experience of watching violence unfold in real time on the Internet is only possible because of the real human beings, phones in hand, who are actually living it.