BOSTON (CBSNewYork) –With the surviving Boston Marathon bombing suspect in police custody Saturday, officials will be trying to determine how and why he and his brother committed the heinous and deadly attack.

Dzhokhar Tsarnaev, 19, was captured Friday night after a shot standoff in the backyard of a Watertown, Mass., home. His older brother, FTamerlan Tsarnaev, 26, was killed in a shootout with police the night before.

President Barack Obama framed what would happen in the investigation to come in his remarks on the capture Friday night, CBS News Senior Correspondent John Miller explained.

“Why did they do this, how did they plan it, and most importantly, did they have help?” Miller said. “Who was responsible for the radicalization? Is it something that perhaps the older brother sought out on the Internet, or did they meet an individual here? So these are questions that go to, are there other people out there, and is it part of a winder network? And those questions are so far unanswered.”

Some experts have characterized the methods allegedly used by the Tsarnaev brothers as “amateur,” as they stayed around after the attack. But others have said their methods were in other ways sophisticated, in terms of being successful in their own eyes, CBS 2’s Dick Brennan explained.

When it comes to the FBI, the key is to fill in the intelligence gaps, Miller explained.

“And that is, why was there no claim to responsibility? Is it because they were waiting to do something else? Why did they have all these additional explosives and devices constructed? Were they waiting to do something else, and if so, what were the targets?” Miller said. “And then we come back to that other question, which comes to the front again – are there other people involved, or is there another network or cell of two people in another city that this is connected to?”

Answering those questions will require an all-out probe of the suspects and their electronic paper trail, Miller said.

“They’re really going to have to crack open the entire world of these two suspects – the dead one and the live one – and go through all of their communications contacts – their entire social network – and say, ‘Who do they know? What do their friends say? What do their families say? What was their travel; when they went? Who did they see? Every phone call they ever made,” Miller said. “That’s what’s happening today.”

Dzhokhar Tsarnaev was not read his Miranda rights, in a public safety exception intended to protect the police and the public from imminent danger. A special interrogation team for high-value suspects will be pressed into service.

“I am fairly confident — and I say that not based on knowledge of his personality, but knowledge the past cases where they sit down a terrorist – whether it was a terrorist whose plot succeeded or failed. In the case of the underwear bomber and others, they seem to have a need to talk at the end of these things. First of all, they have an ideology they want to get, in many cases, to the why. And second of all, a lot of them have a personality trait which is, ‘I want to tell what I did and how clever I was,’” Miller said.

And as to the metro area-wide lockdown in and around Boston while authorities searched for Dzhokhar Tsaranev, Miller said he does not expect a backlash for the decision.

“Nobody has seen anything like it, and that decision to lock down Boston beyond the perimeter where the search was I done that will be picked over and second-guessed and all that,” Miller said. “But I think you know, the judgment of Ed Davis, the police commissioner , who’s very experienced and a great cop, and the mayor – this has to be a joint decision — and the advice of the FBI — for that one day, I don’t think they’re going to be criticized for it. It seemed to be the thing that made sense, and people seemed to follow it.”

Dzhokhar Tsarnaev was being treated Saturday morning at Beth Israel Deaconess Medical Center in Boston. He was last reported in serious condition.

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