People in the crowd started asking, "Is he alive?" One of the officers nodded, yes. Any time a first responder emerged from the street, there was loud applause.
"They finally caught the jerk," said nurse Cindy Boyle, 41. "It was scary; it was tense." She said she knew when police started clapping that everything would be all right.
The suspect, 19-year-old Dzhokhar Tsarnaev, was taken to a hospital after engaging in a firefight with police while hiding out in a parked boat. Earlier that day, about a mile away, his 26-year-old brother, Tamerlan Tsarnaev, had been killed in a gun battle and car chase during which he and his younger brother hurled explosives at police from a stolen car, authorities said.
During the getaway attempt, the brothers killed an MIT policeman and severely wounded another officer, authorities said. The younger brother managed to escape and was found in the boat about a mile away hours later.
"Never in my wildest dreams did I think that this would result in a shootout in Watertown," said Sheamus McGovern, of Belmont, Mass.
McGovern had been startled overnight Friday during a when he heard "what sounded like firecrackers, last night after one, and then pure bedlam." He could hear the helicopters overhead all day.
But after the capture, celebratory bells rang from a church tower. Crowds lined the streets into the center of town. Teenagers waved American flags. Every car that drove by honked. Every time an emergency vehicle went by, people cheered loudly.
Lois Johnson, a 49-year-old attorney, had spent the day inside with her son, so when the celebration started they came outside with a container of cookies they had baked and started handing them out.
Liz Rogers, also an attorney, took one of the pieces of yellow police tape and tied it around her neck like a necklace.
"When you see your town invaded like this, it's stunning," said Rogers, 65. "Everyone in Watertown is just so grateful that he's caught and that we're liberated."
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.
Earlier, the mood was somber. On Boylston Street, three blocks from the site of the marathon explosions on Monday, several dozen people gathered almost in complete silence. Some were crying.
Boston University student Aaron Wengertsman, 19, wrapped himself in an American flag as a silent crowd gathered. He was on the marathon route a mile from the finish line when the bombs exploded.
"I'm glad they caught him alive," Wengertsman said. "I thought people might be more excited, but it's humbling to see all these people paying their respects."
Bathed in the flashing lights from Kenmore Square's iconic rooftop Citgo sign, Boston University juniors Brendan Hathaway and Sam Howes high-fived strangers as they walked down the street.
"This was like our first opportunity to really be outside without feeling like there imminent danger," said Hathaway, a mechanical engineering student from nearby Newton. "It was close to home for me."
In Boston's Dorchester neighborhood, where an 8-year-old boy killed in the bombing lived, people set off fireworks Friday night to celebrate.
Peoples reported from Boston. Associated Press writers Allen G. Breed and Bridget Murphy in Boston contributed.