With the low light, the widest angle is the fastest(gathers the most light) for getting a clear shot. I would surmise the auto would choose the most open aperture(because of the low light) that it could still manage with a shutter speed fast enough to keep things sharp. Then I knew what focus I had to work with and tried to get the whole scene in focus.

I've gotten lazy with my digital cameras, I "used" to know more when I with a less automatic slr.. Maybe Jon or Phil Mislinski will chime in to correct me.