At the end of summer 1944, the residents of small town Mattoon, Illinois, started reporting strange chemical smells in their homes that led to intense symptoms of sickness. Many also reported seeing a figure outside their home that would flee the scene. This figure became known as the Mad Gasser of Mattoon and for weeks, a terrorized town and police force scratched their heads, unable to figure out who was behind these weird attacks that left some Mattoon resident literally paralyzed. 

Sources: The Case of the Mad Gasser of Mattoon by Cindy Ackerman Klickna, Wikipedia, University of Illinois Library, American Hauntings The Mad Gasser of Mattoon