How are multiple shadows formed?

Multiple shadows are formed when there are many light sources. Eg. a night-time football game; the floodlights at each corner of the pitch make the players have 4 shadows. If there are multiple light sources, there will be multiple shadows, with overlapping parts darker, and various combinations of brightness or even colors. The more diffuse the lighting becomes, the softer and more indistinct the shadow outlines become, until they disappear.