The teenage suspect in the Boston Marathon bombings is in custody after being found hiding in a boat in a suburban homeowner's backyard.
He had escaped on foot early on Friday, apparently wounded, after a police shootout that claimed the life of his elder brother, an alleged accomplice.
Three people died and more than 170 were hurt in Monday's bombings.
At a Friday night press conference, US President Barack Obama promised to seek answers on what had motivated the bombers and whether they had help.
He spoke just after state police told journalists that the suspect was being treated at a Massachusetts hospital, bleeding and seriously injured with gunshot wounds to the neck and leg.
The breakthrough came less than an hour after authorities lifted a city-wide order for residents to stay indoors, and reopened the transport system, as the trail appeared to have gone cold.
Upon opening the tarp covering the boat, the resident found a man covered in blood in the stern and called police.
Bomb-squad vans and ambulances surrounded the house, while helicopters buzzed overhead.
Officers tossed flash-bang grenades into the boat to disorient the fugitive.
Police said they exchanged gunfire with the suspect for about an hour before moving in and seizing him.
A crowd near the scene cheered as he was taken into custody.
The property was apparently not searched earlier on Friday as police went door-to-door in Watertown.
Boston Police Department tweeted: "CAPTURED!!! The hunt is over. The search is done. The terror is over. And justice has won. Suspect in custody."
Thousands of Swat team officers had earlier scoured the streets all day in a manhunt that virtually shut down the city.