The dramatic end to the manhunt came when a Watertown man, cooped up in his house all day because of a "shelter in place" order, finally stepped outside when the order was lifted.
David Henneberry soon noticed the tarp covering the boat in his backyard was flapping in the wind and a retention strap was cut. He also noticed a small amount of blood on the tarp.
"He basically stuck his head under the tarp, noticed a pool of blood," Henneberry's stepson Robert Duffy told CNN.
Henneberry called 911, Duffy said.
Authorities arrived and evacuated Duffy's stepfather. Using a bullhorn, they called out to the suspect: "Come out with your hands up."
The man refused.
"We used a robot to pull the tarp off the boat," David Procopio of the Massachusetts State Police said. "We were also watching him with a thermal imaging camera in our helicopter. He was weakened by blood loss -- injured last night, most likely."
A gunfight ensued, with more than 20 rounds fired.
Authorities eventually rushed the boat and took the teen into custody.
Cheers and mourning
As word of the arrest spread, hundreds of residents swarmed the streets of Watertown and Boston, surrounding police cars and cheering them on.
But the celebrations were tempered by the deaths of four people this week, all allegedly by the hands of the Tsarnaev brothers.
Three spectators were killed in the marathon bombings, and Collier, the MIT police officer, was fatally shot early Friday. At least 57 people remained hospitalized Saturday afternoon, including three in critical condition, according to a CNN count.
On Saturday night as Collier's body was driven from the morgue to a funeral home, Boston-area police officers and firefighters lined the route to pay respect to their slain colleague.
The family of 8-year-old Martin Richard, who was killed in the bombings, issued a statement thanking the authorities and members of the public who helped track down the two suspects.
"None of this will bring our beloved Martin back, or reverse the injuries these men inflicted on our family and nearly two hundred others," the Richard family said. "We continue to pray for healing and for comfort on the long road that lies ahead for every victim and their loved ones."
'Boston Stands as One'
Boston sports teams Saturday honored victims of the attacks.
The Boston Red Sox planned a special pre-game ceremony at their Saturday game against the Kansas City Royals, which was played amid heightened security at Fenway Park. Their Friday night game against the Royals was postponed because of the city lockdown and will be played Sunday, the team said.
The Boston Bruins hockey game against the Pittsburgh Penguins, originally scheduled for Friday night, was rescheduled for Saturday afternoon.
The Bruins and Penguins, along with the Red Sox, all plan to auction their Saturday jerseys to support the bombing victims.
Limited-edition T-shirts reading "Boston Stands as One" are being sold by the Boston Celtics to support the victims. Players planned to wear some of the shirts while warming up for Saturday's game, the team said.
The Tsarnaevs' uncle Ruslan Tsarni said their alleged actions were abhorrent.
"You put a shame on our entire family -- the Tsarnaev family -- and you put a shame on the entire Chechen ethnicity," Tsarni said.