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The photos, videos and texts also replace what are, by now, sickeningly familiar media coverage tropes — shots of students marching out of a school with their hands up; parents and onlookers sobbing behind yellow police tape; helicopter footage from overhead surrounded by cable news banners announcing death tolls as breaking news.

While those images are deeply affecting — and can themselves trigger copycat attacks — they’re at a remove from the live terror. Lots of media coverage begins only after the shooting stops.

Messages from students living through an attack are particularly compelling. In one text message exchange with his father published on Twitter by a Parkland survivor, a student tells his parents he loves them and asks, “There’s screaming nearby … what’s going on?” and “where is he?” In a separate text exchange, the same student tells his mother “so many different things are being said I have no idea where he is … I’m scared.”

Parkland senior Demitri Hoth explained the disorienting experience of reading about his own mass shooting attack in real-time on The Washington Post’s site. “Having a phone was a double-edged sword. You had access to information … on the other edge, I guess, you could say it was very, very scary, because we were receiving videos on Snapchat: People on the floor dead. People being shot, people that were already shot, people that were bleeding out.”

Ultimately, Mr. Hoth shared his own group text messages with The Post to add his own messages to show how the instant connection — to friends inside the school and loved ones outside — acted as a lifeline.

But too often links end up broken or accounts are deleted and these eyewitness records deserve to be collected. Universities, government archives and museums should rise to meet the challenge. Already, local museums are working to preserve the makeshift memorials at sites of gun violence. But the wave of school shootings are a national, uniquely American phenomenon, one that is worthy of study at the nation’s leading cultural institutions. Maybe tech companies themselves have some answers for the retention and preservation problem.