Dzhokar Tsarnaev, 19, was reported to be in no condition to be interrogated the morning after he was pulled, wounded and bloody, from a boat parked in the backyard of a home in Watertown, Massachusetts. The capture came at the end of a tense day that began with his older brother, Tamerlan, dying in a desperate getaway attempt.
Massachusetts Gov. Deval Patrick, speaking outside Fenway Park after appearing at a pre-game ceremony at Saturday afternoon's Boston Red Sox baseball game, said Tsarnaev is in serious but stable condition but is likely "not able to communicate yet."
President Barack Obama said there are many unanswered questions about the Boston bombings, including whether the Tsarnaev brothers - ethnic Chechens from southern Russia who had been in the US for about a decade and lived in the Boston area - had help from others.
"When a tragedy like this happens, with public safety at risk and the stakes so high, it's important that we do this right," Obama said. "That's why we take care not to rush to judgment - not about the motivations of these individuals, certainly not about entire groups of people."
There was no immediate word on when Tsarnaev might be charged and what those charges would be.
U.S. officials said a special interrogation team for high-value suspects would question Tsarnaev without first advising him of his right to remain silent and the right to an attorney, a warning typically given to criminal suspects known as the Miranda rule.
Authorities were invoking a rare public safety exception that exists in cases of immediate danger. The FBI's website says the exception "permits law enforcement to engage in a limited and focused unwarned interrogation" and introduce any statements gathered as evidence in a criminal prosecution. The FBI says "police officers confronting situations that create a danger to themselves or others may ask questions designed to neutralize the threat without first providing a warning of rights."
The American Civil Liberties Union expressed concern about invoking the exception. Executive Director Anthony Romero said the exception applies only when there is a continued threat to public safety and is "not an open-ended exception" to the Miranda rule.
The federal public defender's office in Massachusetts said it has agreed to represent Tsarnaev once he is charged. Miriam Conrad, public defender for Massachusetts, said he should have a lawyer appointed as soon as possible because there are "serious issues regarding possible interrogation."
Dzhokhar Tsarnaev's capture touched off raucous celebrations in and around Boston, with chants of "USA! USA!" Residents flooded the streets in relief and jubilation four days after the twin explosions ripped through the marathon crowd at the finish line, killing three people and wounding more than 180.
"Tonight, our family applauds the entire law enforcement community for a job well done, and trust that our justice system will now do its job," said the family of 8-year-old Martin Richard, who died in the bombing. Also killed in the attack was Lu Lingzi, a 23-year-old student from China, and Krystle Campbell, a 29-year-old restaurant worker.
As Boston returned to normal, the city's beloved baseball team, the Boston Red Sox faced the Kansas City Royals Saturday afternoon in their first home game since the marathon attack. The Red Sox had postponed Friday night's game.
Michael Spellman said he bought tickets to Saturday's game at Fenway Park to help send a message to the bombers.
"They're not going to stop us from doing things we love to do," he said, sitting a few rows behind home plate. "We're not going to live in fear."
The all-day manhunt Friday brought the Boston area to a near standstill and put people on edge across the metropolitan area.
The break came around nightfall when a homeowner in Watertown saw blood on his boat, pulled back the tarp and saw a bloody Dzhokhar Tsarnaev hiding inside, police said. After an exchange of gunfire, Tsarnaev was seized and taken away in an ambulance.
"They finally caught the jerk," said nurse Cindy Boyle of Watertown. "It was scary. It was tense."
The bloody endgame came four days after the bombing and just a day after the FBI released surveillance-camera images of two young men in baseball caps suspected of planting the pressure-cooker explosives on Monday at the Boston Marathon finish line.
Queries cascaded in after authorities released the photos - the FBI website was overwhelmed with 300,000 hits per minute -but what role those played in the overnight clash was unclear. State police spokesman Dave Procopio said police realized they were dealing with the bombing suspects based on what the two men told a carjacking victim during their night of crime.
During the long night of violence leading up to the capture, the Tsarnaev brothers carjacked a man in a Mercedes-Benz and released him unharmed, killed a Massachusetts Institute of Technology police officer, severely wounded another lawman and took part in a furious gun battle and car chase in which they hurled explosives at police from a large homemade arsenal, authorities said.
Police said three other people were taken into custody for questioning at an off-campus housing complex at the University of Massachusetts Dartmouth where Dzhokhar Tsarnaev may have lived.
Chechnya, where the Tsarnaev family has roots, has been the scene of two wars between Russian forces and separatists since 1994.
That spawned an Islamic insurgency that has carried out deadly bombings in Russia and the region, although not in the West.
Investigators have not offered a motive for the Boston attack. But in interviews with officials and relatives and acquaintances of the Tsarnaev brothers, a picture has emerged of the older brother as someone embittered toward the U.S. and increasingly vehement in his Muslim faith.
The Russian FSB intelligence security service told the FBI in 2011 about information that Tamerlan Tsarnaev was a follower of radical Islam, two law enforcement officials said Saturday.
According to an FBI news release, a foreign government said that Tamerlan Tsarnaev appeared to be strong believer and that he had changed drastically since 2010 as he prepared to leave the U.S. for travel to a region in that country to join unspecified underground groups.
The FBI did not name the foreign government, but the two officials said it was Russia. The officials spoke on condition of anonymity because they were not authorized to talk about the matter publicly.
The FBI said that in response, it interviewed Tamerlan Tsarnaev and relatives, and did not find any domestic or foreign terrorism activity. The bureau said it looked into such things as his telephone and online activity, his travels and his associations with others.
An uncle of the Tsarnaev brothers said he had a falling-out with Tamerlan over the man's increased commitment to Islam.
Ruslan Tsarni of Montgomery Village, Maryland, said Tamerlan told him in a 2009 phone conversation that he had chosen "God's business" over work or school. Tsarni said he then contacted a family friend who told him Tsarnaev had been influenced by a recent convert to Islam.
Tsarni said the two hadn't spoken since that call.
As for Dzhokhar Tsarnaev, "he's been absolutely wasted by his older brother. I mean, he used him. He used him for whatever he's done," Tsarni said.
Albrecht Ammon, a downstairs-apartment neighbor of Tamerlan Tsarnaev in Cambridge, Massachusetts, said in an interview that the older brother had strong political views about the United States. Ammon quoted Tsarnaev as saying that the U.S. uses the Bible as "an excuse for invading other countries."
Tamerlan Tsarnaev had studied accounting as a part-time student at Bunker Hill Community College in Boston for three semesters from 2006 to 2008, the school said. He was married with a young daughter.
Dzhokhar Tsarnaev was a student at the University of Massachusetts Dartmouth. Students said he was on campus this week after the Boston Marathon bombing.
As of Saturday, more than 50 victims of the bombing remained hospitalized, three in critical condition.