What is the intended effect of juxtaposing the images of the silhouettes with the description of the house's continued paranoia about intruders?

Juxtaposing the images of the family disintegrated into nothingness against the description of the house's security measures is both comic and tragic. The reader is reminded that the purpose of both the atom bomb and the house's security system is to promote the safety of one group of people who feel threatened by another group of people--and yet ultimately, this kind of technology is not the answer. It is terrible and funny that the house continues to attempt to protect a family that has been dead for some time.