On a recent episode of Fringe (Season 2, Episode 6), a shadow entity attacks unwitting victims and turns them into piles of dust (some very good effects here). In this case, the shadowman is an entity from outer space that made its way to earth via a cosmonaut, and it feeds on the trace amounts of radiation people carry in their bodies.
As you’ve no doubt read in this site’s Your True Tales, many people claim to have had sightings or encounters with shadow people. Most of the time they are seen as harmless if unnerving fleeting shadows out of the corner of one’s eye. They certainly have not been blamed for disintegrating folks into gray powder. There have been reports, however, of some shadow people being more than just shadows — having physical effects and even attacking. Check out these stories:

Some suspect that Fringe might have it right — that shadow people are extraterrestrial. What do you think?