by Phoebe Petrovic, Wisconsin Watch

This article was produced for ProPublica’s Local Reporting Network in partnership with Wisconsin Watch. Sign up for Dispatches to get stories like this one as soon as they are published.

Moments before 15-year-old Natalie Rupnow opened fire inside her Madison, Wisconsin, school, killing two people and herself last month, a social media account believed to be hers posted a photograph on X showing someone sitting in a bathroom stall and flashing a hand gesture that has become a symbol for white supremacy.

As news about the shooting broke, another X user responded: “Livestream it.”

Extremism researchers now believe that second account belonged to 17-year-old Solomon Henderson, who police say walked into his high school cafeteria in Nashville, Tennessee, on Wednesday and fired 10 shots, killing one classmate and then himself. Archives of another X account linked to him show that he posted a similar photo to Rupnow’s in his final moments.

If you or someone you know needs help:

• Call the National Suicide Prevention Lifeline: 988
• Text the Crisis Text Line from anywhere in the U.S. to reach a crisis counselor: 741741
• If you or someone you know has been harmed online, you can contact the National Center for Missing & Exploited Children at 1-800-THE-LOST or https://report.cybertip.org/.

While there isn’t any evidence that Rupnow and Henderson plotted their attacks together, extremism researchers who have tracked their social media activity told Wisconsin Watch and ProPublica that the two teenagers were active in the same online networks that glorify mass shooters, even crossing paths. Across various social media platforms, the networks trade hateful memes alongside terrorist literature, exchange tips on how to effectively commit attacks and encourage one another to carry out their own.

The researchers had been tracking these networks for months as part of work looking into growing online extremist networks that have proliferated across gaming, chatting and social media platforms and that they believe are radicalizing young people to commit mass shootings and other violence.

The researchers’ analysis found only a few instances in which Rupnow and Henderson appeared to interact directly. But in the hours, days and weeks that followed the Madison shooting, Henderson appears to have become fixated on Rupnow. He boasted on X that Rupnow and him were “mutuals,” a common internet term for following each other, and shared........

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