It's so that we don't know who to suspect once the event begins.Are we all just going to skip over that couple's son? The artist spent extra detail to never show his face, and we never saw if the villains killed him too.
All of this is non canon, the anime adapted the light novel. The manga is doing, whatever it thinks it's doing with the story.Thanks for the chap. The anime really butchered the story by skipping many important scenes.