>> do they operate on the premise? you've been at multiple of these shootings. the navy yard just a few years ago in washington, d.c. do they operate on the premise that there could be or are multiple shooters, even though all the witnesses are saying, we saw one man. >> absolutely they do. from the very beginning until they confirm there is only one shooter, they operate as though there are more shooters. now, as we talked about earlier, poppy. in most of these cases, it is a male shooter acting alone. and the fbi said these active shooter situations, that is the situation. but law enforcement has to operate under the assumption there is more than one person. so, that is the operating assumption until they can confirm only one person is behind this. just because witnesses are saying they have only seen one shooter, that is not what law enforcement is operating on. >> pamela brown, thank you very much. pamela with me throughout the hour. just to reiterate for you, still an active shooter investigation still going on in chattanooga,