I need a little help. I am in the lobby of the Chinese Embassy where you have to shimmy across the pole to the other side of the upper level of the lobby, drop down and grab a guy to get him to use the retinal scanner. I cannot drop down and get him without getting shot. Heck, half the time, after shooting out all the lights in the whole place, the guy somehow sees me and shoots me. I have tried many ways of doing it, hitting the Y button and then B but I can never drop quietly enough to evade detection. Any help will be greatly appreciated. TIA.