The Bunny Man
If you reside in or near Fairfax, Virginia, you are likely familiar with the Bunny Man's legend. He's the neighborhood bad guy who folks need to watch out for, particularly close to a bridge on Colchester Road.
Legend has it that the region previously housed a secluded asylum for the insane. Despite being transferred, one busload of patients crashed. The most of the patients were once more rounded up, but one escaped. One group of gutted and partially consumed rabbits hanging from a bridge was the sole trace of him that was discovered. Never was the patient located.
A few months later, some neighborhood teenagers go to the bridge to hang out on Halloween. The Bunny Man's reign of terror starts when they are discovered gutted and hanging from the bridge the following day. You face the danger of meeting him if you go to the bridge on Halloween.
There are several gaps in this narrative, not the least of which is the absence of an asylum in the vicinity. However, there is a tale of a man with something on his head attacking a couple in a car and hurling a hatchet at them.
The "something" on his head was transformed into bunny ears by the press, and the narrative developed from there. It didn't take long for the initial story to evolve into a mad man disguised as a rabbit who had escaped from an asylum and was stringing people up, and the rest is history.