I just watched the movie "The Box" and i need a little help understanding certain parts..?

Okay so my friend and i just watched the box and we get the main underlying theme of the movie (put the goodness of humanity over selfishness) but we had some unanswered questions such as: As arlington states when the on is pushed someone you don't know dies (the family before meaning the wife usually dies) but lets say the next family with the box does push the on and the prior family that pushed the on decides not to shoot the wife...who dies? if anyone. And if no one is to die what does that conclude?