I almost feel bad posting this so close to Halloween and potentially spoiling people's fun. But here's the real story of the Bunnyman Legend:
There was a Bunnyman incident. It was nowhere near the Bunnyman bridge though. It happened near the Guinea Road/Twinbrook Road entrance to the Kings Park West subdivision in 1970, when that neighborhood was under construction. An Air Force cadet was parked with his girlfriend in his car there, when a man in a bunny suit threw a hatchet at the car window.
From a Washington Post article recounting the incident:
Air Force Academy Cadet Robert Bennett told police that shortly after midnight last Sunday he and his fiancee were sitting in a car in the 5400 block of Guinea Road when a man "dressed in a white suit with long bunny ears" ran from the nearby bushes and shouted: "You're on private property and I have your tag number."
The "Rabbit" threw a wooden-handled hatchet through the right front car window, the first-year cadet told police. As soon as he threw the hatchet, the "rabbit" skipped off into the night, police said. Bennett and his fiancee were not injured.
Police say they have the hatchet, but no other clues in the case. They say Bennett was visiting an uncle, who lives across the street from the spot where the car was parked. The cadet was in the area to attend last weekend's Air Force-Navy football game.
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Two weeks later, the Post ran second story about another incident in the same area in which a construction company security guard confronted a man in a bunny suit chopping a porch post of a newly constructed home.
This paper by a Fairfax County librarian has the complete story of the bunnyman legend, along with the real story that spawned the legend. It is a very interesting read:
http://www.fairfaxcounty.gov/library/branches/vr/bunny/bunny.htm