this is the interface point where u.s. personnel, they are -- this is where the gate that they were talking about, where u.s. personnel kind of have this very dangerous moment where they have to do a physical search of each person before they are allowed to pass through and enter the airport. and here is why yesterday general mckenzie explains that point is so dangerous. >> this is close up war. the breath of the person you are searching is upon you. while we have overwatch in place, we still have to touch the clothes of the person that is coming in. >> this video that we're showing right here shows just what the general is describing. video taken by pbs correspondent jane ferguson days before the blast. you could see just how close, how dense, the crowds of afghans and u.s. troops are. they are literally touching each other. joining me right now is award winning correspondent for pbs and news hour jane ferguson. thank you for coming in.