stuck in a school with my classmates (and a zombie horde)

no one really knows how it started.
the apocalypse, i mean.
some say it first began in a lab. the zombies were engineered, created to take out vicious enemies. kept secret. but then, it was too late, and after..
well, you know what happened.
others murmur that it was some cruel trick, some illusion.
but i have a different opinion.
an odder one.
you may not believe me. in fact, most of you may not believe me.
in my opinion, it all began in the seventh grade boys' locker room on the lower gym floor.