One of the escaped prisoners has a pump-action shotgun. We see her work the slide and supposedly chamber a round of ammunition. A few minutes later we see her do so again to threaten the son, without having fired the weapon in between. Had it been loaded, it would have ejected the unfired round, but no round was ejected.
When Sally and Jeff sprint through the forest, they run full force across a downed tree to get over a body of water. They were obviously running across a bridge hidden behind the tree.