WATERTOWN, Mass. (AP) -- For just a few minutes, it seemed as if 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 19-year-old -- whose older brother and alleged accomplice was killed earlier Friday morning in a wild shootout in suburban Boston -- was in serious condition Saturday at a hospital protected by armed guards, and he was 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 persuade the suspect to get 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 Friday 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.
Celebratory bells rang from a church tower. Teenagers waved American flags. Drivers honked. Every time an emergency vehicle went by, people cheered loudly.
"They finally caught the jerk,'' said nurse Cindy Boyle. "It was scary. It was tense.''
Police said three other people were taken into custody for questioning at an off-campus housing complex at the University of Massachusetts 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.
Queries cascaded in after authorities released the surveillance-camera 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.
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 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 gunfire left her huddled on the bathroom floor on top of her young son.