Somthing I Saw in the Sky Last Night

Okay, I was shooting my BB Gun in my back yard yesterday afternoon and I was aiming it up over the fence because theres an office complex out there and I like to shoot it. When I looked upward at the sky I noticed this weird thing in the that had wings that looked like triangles but the points were rounded. Its wings seemed very fluid in there movment. My first thought is that it was a plastic bag but it was going really fast. Then I thought It was a Bird, but it was flying so and fast that it couldnt have been a bird and plus it didn't look like any type of bird I've ever seen. Then I thought it was a plane but then it hooked a big time U-Turn and flew into a cloud, And never came out. I waited and waited and it never came out.
I know it sounds crazy but it really happened. Can anybody tell me what it was?

probably a drone spy craft sent to check out somebody shooting a gun at a secret NSA office building.Get ready for the Visit.