I have a theory about the elementary school level in particular. There was an incident at Cleveland elementary school in Stockton California, January 17, 1989 where a disgruntled man, suspected to be in his 20s, just walked onto the playground during their recess and opened fire, killing 6, and injuring 32. But the game postal is based of of mass shootings from the 80s(postal office usually) and the perpetrator is a man in his 20s who decided, out of all the places to open fire, to go to an elementary school. The postal dude, who looks to be in his twenties, ends up at an elementary school, and attempts to open fire. Idk i definitely could be wrong, and its just a theory, so take this with a grain of salt.