Walls shook, windows rattled and the ground moved shortly before 10 p.m., Wednesday evening. The event resulted in startled panic among some and blew up social media with those searching for answers.

Spencer Police Chief Mark Warburton said, “When I looked back at the calls for service, dispatch just made up one call for service but noted that she had received several calls.”

Clay County Sheriff Chris Raveling admitted he had “no idea what caused it.”