It's a little dead and out of focus, but it resembles one from the shiner family...Red or Golden Shiner. I'm not one to bet against Bill D. So, I'm gonna lean towards Mike's suggestion of the gizzard shad.

No dead fish found in the pond? Found just past the spillway and ensuing stream? Are you sure they came from the pond? Do you have a minnow population in the pond?

My guess is that you had some of the rain that we here in Missouri have received and caused an exodus of fish/minnows from your pond and the overflow "atmosphere" was a bit too violent or inhabitable for the little fishes. Just a guess really!

Fish on!,
Noel