Copycat extremism drives deadly violence in U.S., San Diego mosque attack highlights risk
Two teenage attackers killed three men at a San Diego mosque, livestreamed the attack, and left a 75-page manifesto. Experts say it fits a growing online-driven pattern of copycat, hate-motivated violence where shooters imitate earlier attacks and radicalize through digital networks, often transcending traditional political boundaries; federal warnings cite nihilistic violent extremism online.