Sounds like...ergotism!
Useful urls:
https://io9.gizmodo.com/this-fungus-was-a-medieval-mass-murderer-1711876237
https://www.amazon.com/Day-St-Anthonys-Fire/dp/B000QB63Z4/ref=sr_1_1?ie=UTF8&qid=1510578494
Sounds like these people are rabid. Put them down when found.