take devices out of their head. i go back to just a few years ago, just a few miles from me aaron alexis over at the washington, d.c. navy yard was, in his mind, being guided by electromagnetic pulse. and so go ahead. pete: ron, what triggers then further investigation or maybe no fly lists? at what point do you say okay this guy is hearing isis. watching videos. does somebody get evaluated and cleared? do they get put on a list? what are the possibility. >> the fbi's choices here are actually very limited. the fbi is limited by guidelines that our attorney general approved guidelines that limit what the fbi can do. to start a case, to really start an investigation on someone, you basically need two things. one, you need a lawful purpose. so they can't start an investigation because they don't like their neighbor or had a road rage accident on the way in this morning.