Fixed-wing aircraft that went to this location, they tracked the bombs being dropped by that aircraft, saw explosions and then saw civilians reacting in ways that were consistent with the nerve agent attack. so that's the first step. the u.s. has to prove or convince the president that they know who was responsible and that already seems to be under way. the next step, once you have this chain of culpability, would be to present the options to the president. we've also learned that almost since the moment this attack took place, for the last 48 hours or so, national security officials have bee...