Washington DC Ghost Photo

Ty sent us this crazy ghost photo taken while on a school field trip to Washington, DC. We couldn't explain it or make sense of it, whether it is a double-exposure, etc. Well, we got help and it is now solved (see below):

"I believe this may be a picture of a ghost. I took it a few years ago on my eighth grade trip to Washington, DC."

Update:
Trixxie81, a member of the Angels & Ghosts Forum helped us to figure out what this anomaly is:

"The anomaly in the middle of the photo really looks like a pair of sneakers to me. My boyfriend has the same pair! I can't explain how that happened, but the entire pic looks more like camera malfunction than a ghost."