UPDATED 11:48 A.M.: Second Boston Marathon bombing suspect remains hospitalized | Investigators prepare case | Motive unknown | Watertown police chief: "These two acted together and alone"
With one suspect in the Boston Marathon bombings dead and the other apprehended, authorities are now preparing charges against the survivng suspect and probing the motive for the attack.
The massive manhunt that locked down greater Boston came to an end shortly before 9 p.m. Friday after a man emerged from his Watertown home and noticed blood on the boat in his sideyard. The man lifted a tarp to found a seriously wounded 19-year-old Dzhokhar A. Tsarnaev, inside.
Law enforcement took Tsarnaev into custody; his older brother and alleged accomplice, 26-year-old Tamerlan, was killed earlier Friday in a wild police shootout in suburban Boston.
Many questions remained: What was the motive? Was it part of a larger plot? Were there other bombings planned? Investigators were beginning to find answers today.
"From what I know right now, these two acted together and alone," Watertown police chief Edward Deveau said on CNN this morning. "I think we got our guys."
Tsarnaev was taken by ambulance to an area hospital and remains in serious condition. Federal authorities said a special interrogation team for high-value suspects would question him without reading him his Miranda rights, invoking a rare public safety exception triggered by the need to protect police and the public from immediate danger.
The investigation "to seek answers and justice" will continue, FBI director Robert Mueller said in a statement. The University of Massachusetts Dartmout, where Dzhokhar was a registered student, remained closed Saturday due to the investigation, the university said.
Investigators need to "evaluate a tremendous amount of evidence" before formal charges can be filed, said Carmen Ortiz, the U.S. attorney for Massachusetts.
Deveau said police and the FBI still have not collected evidence from the boat where the second suspect was hiding. It isn't known whether he had explosive devices with him there when he was captured.
"We haven't been into that boat, we don't know what's in that boat," Deveau said.
The public-safety exception has been used in other high-profile terror attacks, like the attempted bombing of Times Square in May 2010. It means authorities can interrogate Tsarnaev for a short time without advising him of his rights to have an attorney or remain silent.
The capture of Dzhokhar Tsarnaev elated Boston, with crowds chanting "USA, USA." Residents flooded streets in relief and jubilation.
"CAPTURED!!! The hunt is over. The search is done. The terror is over. And justice has won. Suspect in custody." Boston police tweeted on their official Twitter account.
The two are suspected of planting and detonating crudely made, shrapnel-laden, bombs fashioned from pressure cookers and left on a sidewalk on Boylston Street Monday as runners made their way to the finish line in the famed Boston Marathon.
The blasts killed three, including an 8-year-old boy, and left more than 180 hurt – some severely wounded.
Dzhokhar and Tamerlan Tsarnaev were identified as ethnic Chechens from southern Russia who had been in the U.S. for about a decade and were believed to be living in Cambridge, just outside Boston.
In his weekly address on Saturday morning, President Barack Obama praised the emergency responders, doctors and "big-hearted people of Boston" who showed "heroism and kindness; resolve and resilience; generosity and love" this week.
Since Monday, Obama said, "the world has witnessed one sure and steadfast truth: Americans refuse to be terrorized."
The president added: "If anyone wants to know who we are; what America is; how we respond to evil and terror -- that's it. Selflessly. Compassionately. And unafraid."
In an interview Friday afternoon, an aunt of the suspects said the older brother recently became a devout Muslim who prayed five times a day, and she doesn't believe the brothers could have been involved in Monday's attack.
The international law enforcement agency INTERPOL had issued "an international security alert, or Orange Notice, detailing the features of the improvised explosive devices used in the Boston marathon bombings to assist law enforcement across its 190 member countries detect any similarly configured bombs," the agency said on its website.
"We're talking about three dead people, 100-something injured, and I do not believe, I just do not believe our boys would do that ... I don't know them in the way that they could be capable of this," Maret Tsarnaeva told reporters in Toronto.
But she said Tamerlan was married and had a 3-year-old daughter in the U.S., she said.
"He has a wife in Boston and from a Christian family, so you can't tie it to religion," she said.
The suspects' father, in an interview with a television station where he lives in the Russian province of Dagestan, called police who killed his son "cowards."
Anzor Tsarnaev also said "someone framed [my sons]."
"I don't know exactly who did it. But someone did," the father said. "And being cowards, they shot the boy [Tamerlan] dead. There are cops like this."