What I don't understand is why did he leave the rifle around a tree, assuming if the FBI is telling the truth?
He couldn't have walked far carrying it, because everyone was looking for a person with a gun. Maybe he couldn't find a good place to hide it, and didn't want to waste time looking for one. Or perhaps he left it in a place that would suggest he was headed in a specific direction. He would then go off on a different tack.