1998 East Java ninja scare
The 1998 East Java ninja scare was an outbreak of violence in East Java, Indonesia. The local population believed they were being targeted by sorcerers following the deaths of cattle, and in response, unidentified vigilantes, which people described as ninjas due to their all-black clothing, attacked and killed residents they suspected to be sorcerers, including religious clerics.
Source: Wikipedia — 1998 East Java ninja scare (CC BY-SA 4.0)