Their father, Anzor Tsarnaev, said in a telephone interview with The Associated Press from the Russian city of Makhachkala that his younger son, Dzhokhar, is "a true angel."
He said his son was studying medicine. "He is such an intelligent boy. We expected him to come on holidays here," the father said.
The city of Cambridge announced two years ago that it had awarded a $2,500 scholarship to Dzhokar Tsarnaev, who was listed as a senior at Cambridge Rindge & Latin School, a highly regarded public school whose alumni include Matt Damon, Ben Affleck and NBA star Patrick Ewing.
The images released by the FBI depict the two young men walking one behind the other near the marathon's finish line. Richard DesLauriers, FBI agent in charge in Boston, said Suspect No. 2 in the white hat was seen setting down a bag at the site of the second of two deadly explosions.
Authorities said surveillance tape recorded late Thursday showed Suspect No. 2 during a robbery of a convenience store in Cambridge, near the campus of MIT, where a university police officer — 26-year-old Sean Collier — was shot to death while responding to a report of a disturbance.
From there, authorities said, the two men carjacked a man in a Mercedes-Benz, keeping him with them in the car for half an hour before releasing him at a gas station in Cambridge. The man was not injured.
The search for the vehicle led to a chase that ended in Watertown, where authorities said the suspects threw explosive devices from the car and exchanged gunfire with police. A transit police officer was severely wounded, authorities said.
Doctors at a Boston hospital where Tamerlan Tsarnaev died said they treated a man with a possible blast injury and multiple gunshot wounds. Authorities gave no details on how his younger brother escaped.