Continuity mistake: At the start Edgar smashes his car up and kicks his window out and jumps out leaving a bit of glass in the window frame. However after the camera changes, the 2 bits of glass have disappeared. (00:01:05)
Continuity mistake: As Anna and Mitch get trapped in the silo, various sharp and pointy tools begin to fall on them (a pitchfork, circular saw blades, nails, etc.), but when Ryan finally pulls the lever and the silo door bursts open, they all disappear. Only the wheat and the trapped duo can be seen "flowing" out.
Answer: Spoilers: As revealed at the end, Halloran is a crooked cop who has a past connection to Edgar. Edgar therefore wanted him there, since he presumably assumed Halloran could help him out of this jam. It's also possible that Edgar's tape instructed him to find Halloran, but we can't know this for certain, since it wasn't on-screen.
TedStixon