To begin, I love Bette Davis. I started this movie once, but was unable to finish it so I am glad I'll have the opportunity to watch it again.
The moon seems to be very symbolic in this scene. It is at first beautiful,peaceful, shining light on happy citizens who are playing beautiful music; then it is covered by clouds, creating an ominous environment after the murder. And finally, the moon reveals itself from the clouds to shine light, not in a cheerful and nurturing way, but to reveal what she has done by showing her shadow over the dead body. Very powerful cinematography and use of symb