Terrifying roar caught on video by rock hounder in Colorado

This unexpected video from Finding Treasure in Colorado is really interesting because this clip is an isolated piece of a larger video was recorded when he was out searching for rocks. At the start of the video he was talking about the rain not being bad enough to stop him from digging but he is interrupted by a massive roar in the distance. His facial reaction looks genuine and he goes on to say that THAT was enough to get him to move on. Check this out!