Dzhokhar -- the brother who was wearing a white hat in the surveillance photos from the marathon -- got away when he drove the SUV through a line of police officers at the end of the street, Kitzenberg said.
Law enforcement sources told NBC News that blood found at the scene suggested Dzhokhar may have been wounded in the gun battle.
Whatever they thought they could achieve, they've already failed." Tsarnaev will be questioned by a federal team called the High Value Detainee Interrogation Group, which includes officials of the FBI, CIA, and Defense Department, an Obama administration official said.
His apprehension capped a manhunt that had the city of Boston and its suburbs on total lockdown after the execution of a college campus patrol officer, a carjacking and the death of Tsarnaev's 26-year-old brother, Tamerlan, during a 200-bullet confrontation with cops.
"They also had what looked like a pressure-cooker bomb. Donahue, 33, was seriously injured during the pursuit.
Authorities said he underwent surgery at Mount Auburn Hospital.
As the duo sped in his car toward Watertown, a police chase ensued and they tossed explosive devices out the window, officials said.(: Social Media's Threat to Manhunt) Watertown was the epicenter of the search.Frightened residents were trapped inside as convoys of heavily armed officers and troops arrived by the hour and snipers perched on rooftops and in backyards.At the first, they put in the wrong number; at the second, they took out 0 and at the third, they were told they had exceeded the withdrawal limit, the source said.The carjacking victim was released unharmed at a gas station in Cambridge, sources said.When police finally gave residents the OK to venture outside, some cheered as they stepped outside, only to be swept back inside when shots rang out, and police converged on Tsarnaev's hideout.An administration official said Tsarnaev was not read his Miranda rights and could be questioned without them for up to 48 hours under a special legal exception used in cases where public safety is at stake.Among them, he said: "Why did young men who grew up and studied here as part of our communities and our country resort to such violence?" Authorities are also not sure of a motive or whether the suspects had help.Kitzenberg said he saw the firefight end when Tamerlan Tsarnaev ran toward the officers and ultimately fell to the ground.Tamerlan -- the man in the black hat from FBI photos released six hours earlier -- had an improvised explosive device strapped to his chest, law enforcement officials said.