Fallen MIT Officer Remembered; "An Investigation On Steroids"
TAPPER: Welcome back to THE LEAD. For 26 years, all he ever wanted to do was to become a police officer. Sean Collier was mere months away from achieving his dream when one year ago today two men ambushed him in his car on MIT's campus. Those two men we would later learn were the Boston marathon bombing suspects. Today, Boston, Cambridge, and the MIT officers with whom Sean served came together to honor his sacrifice.</s>JOHN DIFAVA, MIT POLICE CHIEF: Sean was truly one of the brave ones. He made the ultimate sacrifice and he did it for us.</s>TAPPER: Sean Collier's death was one of four in a week-long nightmare that ensnared an entire city in terror. Now we are going to let you see a look back at what has happening behind the scenes as the Boston PD worked around the clock to identify and capture the suspects.</s>TAPPER (voice-over): The new construction and welcoming storefronts can't make former police commissioner, Ed Davis, forget what happened here last year. As we retrace the steps of the Boston marathon bombing, he shares new details about what he calls an investigation on steroids. The first bomb detonated killing Crystal Campbell and wounding scores of others.</s>UNIDENTIFIED MALE: The first bomb went off at the beginning of the construction site at the bay of that building.</s>TAPPER: But it was the second site that proved most destructive, bringing the number of wounded into the hundreds and taking two more lives, Martin Richard and Lingxi Lu.</s>EDWARD DAVIS, FORMER BOSTON POLICE COMMISSIONER: They were still bringing victims from the scene when I arrived here.</s>TAPPER: Commissioner Davis got to work securing the area and anticipating another bomb at any moment.</s>DAVIS: Al Qaeda usually hits in three so we expected there to be a third device here.</s>TAPPER (on camera): So you thought this was al Qaeda?</s>DAVIS: Sure. You have to think that as a possibility. These devices were clearly made by somebody who wanted to kill and maim a lot of people.</s>TAPPER (voice-over): Investigators were forced to immediately pour over every potential clue and there was no shortage. (on camera): So we're in this era where everybody has a camera. There are cameras all over the place. Did you suffer initially at least from too much information, too many photographs?</s>DAVIS: Yes, I think that was really an issue. They sent so much information in so quickly that our computers crashed. It was overwhelmed.</s>TAPPER (voice-over): But it was this camera that provided the critical identification of Dzhokhar Tsarnaev. Investigators then traced his movements in reverse and found Tamerlan.</s>DAVIS: It was the events leading up to the blast and going back camera by camera, we were able to put them together.</s>UNIDENTIFIED MALE: Suspect one and suspect two.</s>TAPPER: Once police released these images of the suspects, they hoped that the public would identify him but just hours later --</s>ERIN BURNETT, CNN ANCHOR: MIT, Massachusetts Institute of Technology is reporting gunshots.</s>TAPPER: The Tsarnaev brothers allegedly killed campus police officer, Sean Collier, and hijacked a vehicle to escape. Then came a second pivotal clue.</s>DAVIS: Around midnight the whole thing ripped open. The hijacking victim got to the phone and told us that he had been hijacked by two men that said that they were responsible for the bombing. We were able to track that car through a GPS system and very quickly Watertown came up with a vehicle.</s>TAPPER (on camera): The Boston Police Department is asking residents of Watertown to stay indoors.</s>DAVIS: The phone call that I got was Commissioner, they are shooting at us and throwing bombs. So I was -- I was shocked. I had never heard that in American policing.</s>TAPPER (voice-over): In the chaos of the Watertown shootout, brother Tamerlan was shot by the police and was then ran over by Dzhokhar escaping in a stolen vehicle. Tamerlan died.</s>DAVIS: One of the sergeants from Watertown was actually trying to handcuff Tamerlan on the ground. The sergeant said I tried to drag him out of the way. I knew the car was going to hit him, but he was too big, I couldn't pull him</s>TAPPER: Dzhokhar was apprehended that night. Federal prosecutors will seek the death penalty. (on camera): The Boston PD, the FBI, you all reconstructed the bombs that the Tsarnaevs brought here. How complicated was that?</s>DAVIS: They were complicated devices and the fact that these things went off in such close proximity showed significant planning.</s>TAPPER (voice-over): Complexity in construction and planning that Davis seems to suspect the two brothers could not have done on their own, especially given their suspected ties to extremists.</s>DAVIS: The fact that they were able to pull this conspiracy off and kill and hurt so many people, you have to look at that very closely. There's a lot going on here and it needs to be fully vetted.</s>TAPPER: This year's marathon, this Monday, will be strictly secured and debut a new rule. No backpacks allowed. (on camera): How do you respond to critics who say, in a way, the terrorists are winning on that one?</s>DAVIS: Right. There's no question, Jake, that that will be an inconvenience to people. And people are upset about that. But the truth of the matter is, at this particular point, right now, with what we know about what happened last year and the state of the world, it just is a prudent thing to do.</s>TAPPER: We'll be going back to Boston on Monday for a much happier marathon day, a special live edition of THE LEAD on Patriot's Day from Boston. Tune in at 4:00 p.m. Eastern. Make sure to follow me on twitter @jaketapper and also @theleadcnn. Check our show page at cnn.com/thelead for video blogs and extras. That's it for THE LEAD. I'm Jake Tapper. Have a great weekend. I now turn you over to Wolf Blitzer. He is right next door in "THE SITUATION ROOM."