Here's my theory:
- Miller General Store is closed on July 19 (elderly couple takes Saturday off; they don't really need the money, they're just doing this so they can cope with their retirement).
- Mr. Ingel isn't the name of the principal.
The PA announcement is being made to catch someone, an impostor who doen't go to the school but somehow snuck in. Someone who's not from the same part of the country. That's why the announcer even bothered to put a name in there- because they wanted to catch someone who didn't know what had happened.
They'd encountered this imposter earlier, and he/she'd claimed to have shopped at the store on Saturday (when it's closed) so that's what tipped them off.
In the balance hangs the life of every student in the school.
How to properly understand my response:
http://www.youtube.com/watch?v=eKQOk5UlQSc