let s bring in chief ramsey on that point. chief, you ve been the police chief, the police commissioner in two cities with subway systems, mass transit systems, with densely very populated urban areas. walk us through, in terms of the uniqueness or the special tis of the search now, the challenges of the search, when you have a, a subway system, and b, a densely populated area. video is going to be incredibly important. trains run on schedule. and so they know the route that the train takes. they know what train that time was at what station. they ll be able to check video from all of those stations to try to find when this person got on. and they ll be looking at all the video from the subway station where the train pulled in after the shooting and look at all of that footage again and then try to backtrack, where is this person then going to? he could take off that sweatshirt, get rid of that green vest. obviously, not going to be walking down the street wearing