 Well, a fraction of a second before the three shots are heard aimed at Trump, both snipers duck or appear to be surprised. Now, that's an important observation. Then the lead sniper raises his head above his rifle to get a wider view. Now, this is important because looking through a scope limits your view to about 10 feet or less, depending on the distance and magnification. We don't know what he was looking at before the shots, and it may be likely that