As Media Matters has previously documented:
The QAnon movement was name-checked in a leaked May 2019 FBI document highlighting the emergence of conspiracy theory-fueled domestic terrorism threats, and devotees have committed a number of murders, engaged in armed standoffs, and made politically motivated death threats. QAnon followers have vandalized churches, taken police on high-speed chases, and in one case, conspired with fellow followers to commit kidnapping.
Update (9:00 p.m.): This post has been updated with additional information about QAnon-linked violence.