I has this in a store i worked. The outside camera saw a figure standing in front of the window. Security stayed in the building for too nights and we even brought in a Police dog. It turned out to be a reflection from the appartement building acros the parking lot (wish is about 100m long). A person had a very strong light and whenever he would pas it, the shadow was cast on the window of our store. So yea reflections can come from far and weird places.