Police captured the surviving Boston Marathon bombing suspect, found bloodied in a backyard boat after a wild car chase and gun battle that left his older brother dead and the Boston area sealed in an extraordinary dragnet.
The capture of Dzhokhar Tsarnaev ' taken alive, though seriously wounded' lifted days of anxiety for Boston and Americans everywhere, but little was known about the motivation of the ethnic Chechen brothers.
President Barack Obama vowed investigators would solve that mystery. "The families of those killed so senselessly deserve answers," said Obama, who branded the suspects "terrorists."
During a long night of violence Thursday and into Friday, the brothers killed a Massachusetts Institute of Technology police officer, severely wounded another lawman and hurled explosives at police in a desperate getaway attempt, authorities said.
Late Friday, less than an hour after authorities said the search for Dzhokhar had proved fruitless, they tracked down the 19-year-old university student holed up in the boat. He was weakened by a gunshot wound after fleeing on foot from the overnight shootout with police that left 200 spent rounds behind.
Tsarnaev was hospitalized in serious condition, unable to be questioned about his motives.
Boston police announced via Twitter that Tsarnaev was in custody. They later wrote: "CAPTURED!!! The hunt is over. The search is done. The terror is over. And justice has won. Suspect in custody."
Tamerlan Tsarnaev, 26, died in the shootout early in the day. At one point, he was run over by his younger brother in a car as he lay wounded, according to investigators.
The bloody endgame came four days after the bombing and just a day after the FBI released surveillance-camera images of two young men suspected of planting the pressure-cooker explosives that ripped through the crowd at the marathon finish line, killing three people and wounding more than 180.
The two men 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, Massachusetts. But investigators gave no details on the motive for the bombing.