in a crowded market district. police warning everyone to stay down and hide. outside, thousands were fleeing in terror. like three men, with kind of bomb looking belt. a policeman was trying to put himself between these attackers and rest of the people trying to scare them. they shot and killed men who wore fake bomb vests wnt eight minutes of the first emergency call. we believe three suspects are dead. reporter: american intelligence now helping london police. we have a good working relationship with you our ameri colleagues and depend on them to keep the country safe. britain s prime minister outraged. we believe we re experiencing a new trend in the threat we face as terrorism breeds terrorism. but it is time to say enough is enough. reporter: the three terrorists haven t been named.