to go back in if they develop new evidence that he has returned. what they said at the news conference is that his ties are to the watertown area and they do not believe he has any vehicle of his own. they believe he is still in the immediate vicinity. they also indicated that they have had several leads into other parts of massachusetts but at this point, that has washed out. and i think most significantly when asked how they got to these guys, they indicated that by releasing the pictures 24 hours ago and we talked about this on your broadcast last night it can have the effect of forcing them to move or to flee to act in some way that draws attention to themselves. that appears to be what the tipoff may have been, bret. >> bret: catherine, very quickly. what i don't understand yet is how after this fire fight and the bomb throwing, the pipe bombs and the homemade grenades and exchange with police how dzhokhar tsarnaev escapes? how does he get out of that