WATERTOWN, Mass. — For just a few minutes, it seemed like the dragnet that had shut down a metropolitan area of millions while legions of police went house to house looking for the suspected Boston Marathon bomber had failed.

Weary officials lifted a daylong order that had kept residents in their homes, saying it was fruitless to keep an entire city locked down. Then one man emerged from his home and noticed blood on the pleasure boat parked in his backyard. He lifted the tarp and found the wounded 19-year-old college student known the world over as Suspect No. 2.

Soon after that, the 24-hour drama that paralyzed a city and transfixed a nation was over.

Dzhokhar Tsarnaev’s capture touched off raucous celebrations in and around Boston, with chants of “USA, USA” as residents flooded the streets in relief and jubilation after four tense days since twin explosions ripped through the marathon’s crowd at the finish line, killing three people and wounding more than 180.

The jubilation was widespread. The mayor of Boston, which was largely paralyzed during the manhunt Friday, tweeted, “We got him!” And at the home of the New York Mets, fans leapt to their feet and cheered when the news spread during a game against the Washington Nationals.

Hundreds of people marched down Commonwealth Avenue, chanting “USA” and singing the Red Sox anthem “Sweet Caroline” as they headed toward Boston Common. Police blocked traffic along part of the street to allow for the impromptu parade.

The 19-year-old — whose older brother and alleged accomplice was killed earlier that morning in a wild shootout in suburban Boston — was hospitalized in serious condition Saturday, unable to be questioned to determine his motives. U.S. officials 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.

President Barack Obama said there are many unanswered questions about the Boston bombings, including whether the two men had help from others. He urged people not to rush judgment about their motivations.

Dzhokhar and his brother, 26-year-old Tamerlan Tsarnaev, were identified by authorities and relatives 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. Tamerlan Tsarnaev died early in the day of gunshot wounds and a possible blast injury. He was run over by his younger brother in a car as he lay wounded, according to investigators.

During a long night of violence Thursday and into Friday, the brothers killed an MIT police officer, severely wounded another lawman during a gun battle and hurled explosives at police in a desperate getaway attempt, authorities said.

Late Friday, less than an hour after authorities lifted the lockdown, they tracked down the younger man holed up in the boat, weakened by a gunshot wound after fleeing on foot from the overnight shootout with police that left 200 spent rounds behind.

The resident who spotted Dzhokhar Tsarnaev in his boat in his Watertown yard called police, who tried to talk the suspect into getting out of the boat, said Boston Police Commissioner Ed Davis.

“He was not communicative,” Davis said.

Instead, he said, there was an exchange of gunfire — the final volley of one of the biggest manhunts in American history.

The violent endgame unfolded just a day after the FBI released surveillance-camera images of two young men suspected of planting the pressure-cooker explosives at the marathon’s finish line, an attack that put the nation on edge for the week.

Watertown residents who had been told in the morning to stay inside behind locked doors poured out of their homes and lined the streets to cheer police vehicles as they rolled away from the scene.

Police said three other people were taken into custody for questioning at an off-campus housing complex at the University of the Massachusetts at Dartmouth where the younger man may have lived.

“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.

The FBI was swamped with tips — 300,000 per minute — after the release of the surveillance-camera photos, 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.

The search by thousands of law enforcement officers all but shut down the Boston area for much of the day. Officials halted all mass transit, including Amtrak trains to New York, advised businesses not to open, and warned close to 1 million people in the entire city and some of its suburbs to unlock their doors only for uniformed police.

Around midday, the suspects’ uncle, Ruslan Tsarni of Montgomery Village, Md., pleaded on television: “Dzhokhar, if you are alive, turn yourself in and ask for forgiveness.”

Until the younger man’s capture, it was looking like a grim day for police. As night fell, they announced that they were scaling back the hunt and lifting the stay-indoors order across the region because they had come up empty-handed.

But then the break came and within a couple of hours, the search was over. Dzhokhar Tsarnaev was captured about a mile from the site of the shootout that killed his brother.

A neighbor described how heavily armed police stormed by her window not long after the lockdown was lifted — the rapid report of gunshots left her huddled on the bathroom floor on top of her young son.

“I was just waiting for bullets to just start flying everywhere,” Deanna Finn said.

When at last the gunfire died away and Dzhokhar Tsarnaev was taken from the neighborhood in an ambulance, an officer gave Finn a cheery thumbs-up.

“To see the look on his face, he was very, very happy, so that made me very, very happy,” she said.

Authorities said the man dubbed Suspect No. 1 — the one in sunglasses and a dark baseball cap in the surveillance-camera pictures — was Tamerlan Tsarnaev, while Suspect No. 2, the one in a white baseball cap worn backward, was his younger brother.

Chechnya, where the brothers grew up, has been the scene of two wars between Russian forces and separatists since 1994, in which tens of thousands were killed in heavy Russian bombing. That spawned an Islamic insurgency that has carried out deadly bombings in Russia and the region, although not in the West.

The older brother had strong political views about the United States, said Albrecht Ammon, 18, a downstairs-apartment neighbor in Cambridge. Ammon quoted Tsarnaev as saying that the U.S. uses the Bible as “an excuse for invading other countries.”

Also, the FBI interviewed the older brother at the request of a foreign government in 2011, and nothing derogatory was found, according to a federal law enforcement official who was not authorized to discuss the case publicly and spoke on condition of anonymity.

The official did not identify the foreign country or say why it made the request.

Exactly how the long night of crime began was unclear. But police said the brothers carjacked a man in a Mercedes-Benz in Cambridge, just across the Charles River from Boston, then released him unharmed at a gas station.

They also shot to death a Massachusetts Institute of Technology police officer, 26-year-old Sean Collier, while he was responding to a report of a disturbance, investigators said.

The search for the Mercedes led to a chase that ended in Watertown, where authorities said the suspects threw explosive devices from the car and exchanged gunfire with police. A transit police officer, 33-year-old Richard Donohue, was shot and critically wounded, authorities said.

Dzhokhar Tsarnaev ran over his already wounded brother as he fled, according to two law enforcement officials who spoke on condition of anonymity because they were not authorized to discuss the investigation. At some point, he abandoned his car and ran away on foot.

The brothers had built an arsenal of pipe bombs, grenades and improvised explosive devices and used some of the weapons in trying to make their getaway, said Rep. Dutch Ruppersberger, D-Md., a member of the House Intelligence Committee.

Watertown resident Kayla Dipaolo said she was woken up overnight by gunfire and a large explosion that sounded “like it was right next to my head … and shook the whole house.”

“It was very scary,” she said. “There are two bullet holes in the side of my house, and by the front door there is another.”

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.

Dzhokhar Tsarnaev was registered as a student at the University of Massachusetts Dartmouth. Students said he was on campus this week after the Boston Marathon bombing. The campus closed down Friday along with colleges around the Boston area.

The men’s father, Anzor Tsarnaev, said in a telephone interview with AP from the Russian city of Makhachkala that his younger son, Dzhokhar, is “a true angel.” He said his son was studying medicine.

“He is such an intelligent boy,” the father said. “We expected him to come on holidays here.”

A man who said he knew Dzhokhar Tsarnaev and Krystle Campbell, the 29-year-old restaurant manager killed in Monday’s bombing, said he was glad Dzhokhar had survived.

“I didn’t want to lose more than one friend,” Marvin Salazar said.

“Why Jahar?” he asked, using Tsarnaev’s nickname. “I want to know answers. That’s the most important thing. And I think I speak for almost all America. Why the Boston Marathon? Why this year? Why Jahar?”

Two years ago, the city of Cambridge awarded Dzhokhar Tsarnaev a $2,500 scholarship. At the time, he was a senior at Cambridge Rindge & Latin School, a highly regarded public school whose alumni include Matt Damon, Ben Affleck and NBA Hall of Famer Patrick Ewing.

Tsarni, the men’s uncle, said the brothers traveled here together from Russia. He called his nephews “losers” and said they had struggled to settle in the U.S. and ended up “thereby just hating everyone.”