more violence. shots ring out at m.i.t. in cambridge. 26-year-old campus police officer sean collier is shot and killed while sitting in his vehicle. there is speculation that the incident is connected to the bombers, but no one knows for sure. it was a routine call of a disturbance. he s responding, gets there, and within seconds he s shot in the back of the head twice, excuse style. he had no chance to defend himself. for officers, there s no time to reflect on the loss. within minutes, they receive a report of an armed carjacking of a black mercedes suv in another part of cambridge. the victim who does not want to be identified, would later tell police that he was held at gunpoint by two men. according to this owner of the car, he escaped. he claims that they told him they were the boston marathon bombers, that they had shot a campus policeman, but they were
gunpoint by two men. according to this owner of the car, he escaped. he claims that they told him they were the boston marathon bombers, that they shot a campus policeman but they were not going to kill him because he was not an american. reporter: some of the suspects movements during the carjacking are caught on camera. suspect number two is seen here on this atm s security cam. they did take the victim s atm card and went to an atm machine and withdrew $800. reporter: suspect number two is later seen on a security camera at this shell gas station. it s here that the carjacking victim escapes unhurt but he leaves one thing behind. we got notified that the victim s cell phone was left in the carjacking vehicle. so the cambridge police were actually able to ping the phone and pick up where its location was. reporter: it leads them to watertown, massachusetts. just after midnight, police
apply here, use of a weapon of mass destruction, which is the federal law version of what a bomb is, if death results, then that is a capital offense. the government could seek the death penalty. massachusetts is a state that does not have the death penalty. so the only death-eligible charge here would be the federal offense, even though four people were killed, the government alleges, the three victims of the. bog and the campus policeman. okay. in terms of the investigation, where does that stand now? what are the most prom neinent angles that are being pursued? these main questions are really the ones that have been true ever since the discovery of who these two people were. and the directions that they re headed in are really going to be the same here for weeks. so the investigation is not going to be, you know, taking sudden turns. the main questions are how and
to the fbi. whether it is just as a result of the boston bombing or whether there was something else that had their interest, i don t know the answer to that. nbc pete williams, again, reporting these two are bothers. one 19 years old. he is the one still at large. he is the one who in the pictures we have been showing wearing the white hat and the one that planted the second bomb, a cambridge resident. the other is 20 years old. he perished and law enforcement authorities found him with an ied attached to his body. pete, do i have that all correct? that s right. that s right. he s on the phone. no, that s all right. i think it bears repeating that, you know, this did not start because the fbi was moving in on them. this started because five hours after the fbi showed their picture, they decided apparently to try to make a run for it or, you know, bring it to an end or whatever. they rob a 7-eleven and shoot a campus policeman and it takes off from there. but the fbi was not
the two men behind the marathon bombing. do we know anything about the owner of that suv who was later released unharmed after spending half an hour with the two brothers? we do. we know who he is, we ve decided not to name him since he s an innocent victim in all of this. but yes, he was just someone who happened to be driving around, unlucky to be in the place where they decided to do the carjacking. but you re right, authorities have said during the carjacking they told him they had just shot and killed a campus policeman in cambridge and they were the boston marathon bombers. pete williams, nbc news justice correspondent, thank you very much. we re going to bring in now senior executive producer for nbc s investigative unit, richard esposito. a fluid and changing situation. it sounds as if dzhokah tsarnaev may be holed up in a house. how do investigators handle this at this point? his uncle was out in public making a statement saying his father told abc news that he thought his