Jessica had stated the cook was selling the kitchen supplies because the truck had arrived empty and Jessica had seen the prisoners unloaded it to use the kitchen stuff as a barricade. At the end, the guards are seen reloading the truck instead of returning the items to the kitchen dock behind them as the warden and Jessica walk by.
During the riot, the prisoners (particularly hotheaded Kathryn) like to "rack rounds," chambering shells into the firing chambers of their pump shotguns - some do it three or four times over the course of the hour. But if a shell is already IN the chamber, it would fly out to make room for the next one. The weapons are obviously empty.
When Jessica writes "The perfect Crime" on the chalk board she does not capitalize the letter"p" in perfect. An English teacher, retired or not would never do this.