Shots fired, a very tense scene, very active. >> all right. all right. mike tobin, thank you so much. we are going to keep following this. a big chase is underway right now in boston. police using everything they can to find this person, after one suspect involved in a shooting where an officer has been killed. we will have much more information on this as approximate becomes available. again, if you are joining us, a big chase underway in boston, following a police shooting at the campus of m.i.t. we want to stress at this point, there is no indication that this is related to the boston bombi...