meeting in italy says the world cannot stand by and watch. state department officials tell cnn yau russia bears responsibility. there is a dossier of responsibility for the nerve action taking shape. according to u.s. officials, assad either knew about this specific attack or had given commanders standing authority to use nerve agent. more chemical sites in western syria likely exists and scientists are still alive who know how to make nerve agent. the u.s. also looking for direct evidence russian commanders on the ground knew about the planned attack. >> and tonight there is a full intelligence investigation into exactly that. how much did the russians know and when did they know it? u.s. officials are saying it was a russian drone that flew over the hospital and where so many