Well, first there were the initial sightings of the Mothman. People described this creature as having red eyes and large wings. Then there were strange electrical problems in the area, like lights flickering. There were also reports of some individuals having disturbing dreams or premonitions after seeing the Mothman. The big event that seemed to tie it all together was the collapse of the Silver Bridge. But again, while it's all part of the story, there's no solid proof that the Mothman had anything to do with it.
In the Mothman Prophecies true story, it began with multiple people in Point Pleasant seeing a strange, winged figure. These sightings created a sense of fear and mystery in the town. There were also reports of psychic experiences among some of the witnesses. As time passed, more and more people claimed to have seen the Mothman or experienced something odd. The Silver Bridge disaster was a major event that some associated with the Mothman. But the whole story is really a blend of local lore, unexplained events, and people's attempts to find meaning in strange happenings. There could be natural explanations for many of the things that happened, like the bridge collapse being due to structural issues rather than some supernatural force.