In the bonus section they show some deleted scenes. One shows a character come by the ranch and let the bad guy out. Without this scene in the movie it's implied that his wife lets him out. However, I didn't see her away from the other two escapees at any time. So when did she come back to the barn and set him free?
shareI know this post is old but I just finished watching the movie so I figured I'd answer. It's not implied that Kathy got him out because she says something along the lines of "I thought I'd have to ditch the kids and come back to unlock you." Plus she was with Erin the entire time of their escape. You're just left to assume that he managed to get himself out. I'm not sure which character would have let him out since everyone else either dead or someone who wouldn't want to have him let out.
------------------
"But it was us baby who were the lucky ones."