Boston Marathon bombing misidentification controversy

After the April 15, 2013 Boston Marathon bombings, Reddit users created the subreddit r/findbostonbombers in an attempt to crowdsource identification of the perpetrators. When the FBI released surveillance images of two suspects on April 18, redditors and other social-media users seized on perceived resemblances and named several innocent people, most prominently Sunil Tripathi, a Brown University student who had gone missing in March. The false accusation spread rapidly across Reddit, Twitter, and into some mainstream coverage, even though Tripathi had no connection to the attack; the actual suspects were soon confirmed to be Dzhokhar and Tamerlan Tsarnaev.

The episode ended tragically: Tripathi's body was later recovered from the Providence River, his death ruled a suicide, and his family endured a wave of harassment during the search. The incident became a defining cautionary tale about online vigilantism and the dangers of crowdsourced investigation. Reddit's then–general manager Erik Martin issued a public apology acknowledging that "online witch hunts" had caused real harm to innocent people, and the platform tightened its stance against posts encouraging the identification of private individuals.