under investigation by the fbi as far back as 2014. the fbi knew that when manafort unexpectedly became chairman of the campaign of donald trump in 2016. >> is there some duty to warn or any sort of -- is there some action that the fbi should take. you are not asked to do background checks for people on political campaigns but when you know of what you know of these folks and ongoing investigations involve with these people seriously matter. >> should something be said. >> in general, it depends on what the facts are that started the investigation and what you learned. the goal is to disrupt the adversary's action. sometimes they'll do a criminal case and locking up the person that's with foreign power, hey, you are hooked up with them, knock it off. sometimes it is a laying in the weeds trying to develop source of information to get close to them.