Boston bombings: A city can exhale WATERTOWN, Mass. - A manhunt that locked down metropolitan Boston for 23 hours ended Friday night when police unleashed a barrage of gunfire and snatched the second suspect in the Boston Marathon bombings from his hiding place in a covered boat in a backyard. Dzhokhar Tsarnaev, 19, was found huddled and covered in blood by officers who stormed the suburban neighborhood after receiving a tip from a homeowner. The suspect's brother, Tamerlan Tsarnaev, 26, had died before dawn Friday in a fierce gun battle with police not far from the same section of Watertown. Only a day earlier, pictures of the two men - wearing baseball caps and carrying backpacks that authorities said held bombs - had been spread across the country in an effort to identify them. Friday night, spectators broke out into applause as an ambulance with the younger brother made its way toward a hospital, and further celebrations broke out in central Boston. "CAPTURED!!!" the Boston Police Department tweeted. The hunt is over. The search is done. The terror is over. And justice has won. Suspect in custody. "The people of Boston will be able to sleep tonight," Mayor Thomas Menino said. President Obama, who watched the arrests unfold on television from the White House residence, congratulated police and federal agents on the intense, four-day investigation that successfully sifted through countless tips and thousands of photos. He pledged that the federal government would not stop its work with the arrests. "Obviously, there are still many unanswered questions," he said. Among them, why did young men who grew up and studied here as part of our communities and our country resort to such violence? How did they plan and carry out these attacks? And did they receive help? Friday's events ended an intense dragnet underway since two closely timed bombs went off during Monday's marathon, killing three people and injuring more than 170. The climactic finale began shortly after 10 p.m. Thursday, authorities said, when the brothers shot a police officer to death at the Massachusetts Institute of Technology, hijacked a sport utility vehicle, then opened fire on pursuing officers with gunshots, explosives and homemade hand grenades, leaving one officer critically wounded. The furious gun battle - with 200 rounds of ammunition exchanged as residents of a Watertown neighborhood crouched in their homes - ended with the elder Tsarnaev dead and the younger, also apparently wounded, fleeing on foot. In scenes rare to modern American law enforcement, city authorities shut down the entire Boston transit system, asked businesses to close, searched trains and urged people to stay home and lock their doors. The search rendered bustling Boston eerily empty - a scary snow day, some Bostonians described it. Hurricanes, natural disasters - a city shuts down. But nothing like this," said Steven Feldman, a lawyer who works in downtown Boston. Boston Police Commissioner Edward Davis concurred, pointing to the dizzying array of ammunition and explosives deployed by the two suspects. "This is the stuff that [for] an urban police department, it's almost unheard of," he said. By nightfall, authorities had decided to lift the advisory to stay indoors, warning that it still might not be entirely safe. But "we cannot continue to lock down an entire city," said Col. Timothy Alben of the Massachusetts State Police. Residents of a 20-block area of Watertown near the shootout began venturing outside, some to go to the store, some for a short walk. Outside, one resident noticed something amiss about the small boat in his backyard. When he lifted a tarp covering it, he found a man covered in blood. He quickly retreated and called 911. A dozen police cars screeched into the neighborhood, witnesses said, followed by hundreds of officers. An FBI hostage rescue team, guided by a helicopter overhead looking for heat signatures, cautiously approached the boat, fearful that the suspect might have more explosives. They used a robotic arm to lift the tarp, officials said. Within minutes, a new barrage of gunfire and stun grenade volleys erupted. "It was pow pow pow pow pow, at least 15, 30 shots," said neighbor Deanna Finn, who dragged her 8-year-old son onto the bathroom floor and threw herself on top of him. She kept flushing the toilet to drown out the noise of the volleys outside. It felt like my entire life, I swear. I never had anything go so fast and so slow at the same time," she said.