Stand Still!
Rather than being shocked about nearly being hit by a flying metal object. Sam was far more concerned about the skill he had just witnessed in front of him. The move that he and Nate referred to as the flash step. This was because whenever they saw the move being used, it really did seem like the user would suddenly flash into a different spot.
More importantly, it was a move that Sam had only seen one person ever perform, the person known as Bloodevolver from the game. However, just because they had only seen one person perform it., didn't mean only one person knew how to.
A teacher most likely needed to teach the person the move, and they most likely taught others. It was possible for one to come up with a skill themselves, but knowing the information about the Bloodevolver they did know, that seemed unlikely.