What was the real beast

On the Director's Cut Bonus Disc is a feature saying that the movie was partially inspired by the book, La Bete de Gevaudan, by French author, Michel Louis. This author researched the actual incident and says that what most likely occurred is that one or two men from a warped noble family were sadists, and that they bred wolf-dog hybrids that they then used to hunt down & kill people for their own sadistic enjoyment. If I remember correctly from the bonus feature, one of the sadist noblemen shot & killed the first beast, probably to belay suspicions about his involvement. The author theorizes that because he so easily killed the beast at close range, when so many others had failed to even find it, it was probably because he was the beast's master and it was waiting for him to command it (i.e. it wasn't attacking him). Regardless, he was imprisoned on some charge, and the killings stopped. Then when he got out of jail, the killings resumed (he probably had a second hybrid).

"No *beep* sh*t lady, do I sound like I'm ordering a pizza?" - John McClane

No one knows. The real Beast of Gevedaun was never taken.

It has also been suggested that it could have been a hyena, though how it ended up in France is anyone's guess.