The sweat on Alex's shirt changes drastically between when he jumps up to the rafters to climb up, and when he actually makes it up to the second floor of the barn.
Before Alex breaks the basement window of the barn there is blood on his bandanna. This blood is not there again until several scenes later.
Alex trips over a dead body in the woods. He takes two things from it, a sledge hammer and a compass. We see him use the sledge hammer but we never see or hear anything about the compass again.