isis and there is one message for them, to stay home and launch attacks. >> the operating assumption here is that this is an act of terrorism. this investigation is now going to be led by counterterrorism command known as so-15. they are one of the most capable counterterrorism outfits in the world. they work very closely with mi-5. they will be going through all sorts of cc-tv, witness statements and investigating this with great intensity. their biggest concern right now, obviously, is this over. they were not commit tal about that. they didn't say whether they have full confidence that this terrorist event is over. >> it doesn't look like it's over yet. christiane amanpour is with us. you've heard the spokesman for the london metropolitan police commander harrington say they are assuming -- they are working