We were watching the bats in the garden last night at sunset...
Me too My wife meanwhile was inside thinking I was batty standing out there with my camera.
Yes, it's a lucky shot using a wide angle lens and the camera's built in flash. I processed the RAW image in DxO PhotoLab 3, using it's PRIME noise reduction algorithm.
Perhaps, somehow, the image was captured using the camera's built in flash but the shadow appears to be cast by a strong light coming from much further to my left than where the camera flash came from.
More importantly, what is the shadow projected on to? Not the clouds, they are too far away.