"I was just waiting for bullets to just start flying everywhere,'' Deanna Finn said.
When at last the gunfire died away and Dzhokhar Tsarnaev was taken from the neighborhood in an ambulance, an officer gave Finn a cheery thumbs-up.
"To see the look on his face, he was very, very happy, so that made me very, very happy,'' she said.
Authorities said the man dubbed Suspect No. 1 -- the one in sunglasses and a dark baseball cap in the surveillance-camera pictures -- was Tamerlan Tsarnaev, while Suspect No. 2, the one in a white baseball cap worn backward, was his younger brother.
Chechnya, where the Tsarnaev family has roots, has been the scene of two wars between Russian forces and separatists since 1994, in which tens of thousands were killed in heavy Russian bombing. That spawned an Islamic insurgency that has carried out deadly bombings in Russia and the region, although not in the West.
The older brother had strong political views about the United States, said Albrecht Ammon, 18, a downstairs-apartment neighbor in Cambridge. Ammon quoted Tsarnaev as saying that the U.S. uses the Bible as "an excuse for invading other countries.''
Also, the FBI interviewed the older brother at the request of a foreign government in 2011, and nothing derogatory was found, according to a federal law enforcement official who was not authorized to discuss the case publicly and spoke on condition of anonymity.
The official did not identify the foreign country or say why it made the request.
Exactly how the long night of crime began was unclear. But police said the brothers carjacked a man in a Mercedes-Benz in Cambridge, just across the Charles River from Boston, then released him unharmed at a gas station.
They also shot to death a Massachusetts Institute of Technology police officer, 26-year-old Sean Collier, while he was responding to a report of a disturbance, investigators said.
The search for the Mercedes 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, 33-year-old Richard Donohue, was shot and critically wounded, authorities said.
Dzhokhar Tsarnaev ran over his already wounded brother as he fled, according to two law enforcement officials who spoke on condition of anonymity because they were not authorized to discuss the investigation. At some point, he abandoned his car and ran away on foot.
The brothers had built an arsenal of pipe bombs, grenades and improvised explosive devices and used some of the weapons in trying to make their getaway, said Rep. Dutch Ruppersberger, D-Md., a member of the House Intelligence Committee.
Watertown resident Kayla Dipaolo said she was woken up overnight by gunfire and a large explosion that sounded "like it was right next to my head ... and shook the whole house.''
"It was very scary,'' she said. "There are two bullet holes in the side of my house, and by the front door there is another.''
Tamerlan Tsarnaev had studied accounting as a part-time student at Bunker Hill Community College in Boston for three semesters from 2006 to 2008, the school said. He was married with a young daughter.
Dzhokhar Tsarnaev was registered as a student at the University of Massachusetts Dartmouth. Students said he was on campus this week after the Boston Marathon bombing. The campus closed down Friday along with colleges around the Boston area, and it remained closed Saturday as law enforcement continued investigating.
The men's father, Anzor Tsarnaev, said in a telephone interview with the AP 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,'' the father said. "We expected him to come on holidays here.''
A man who said he knew Dzhokhar Tsarnaev and Krystle Campbell, the 29-year-old restaurant manager killed in Monday's bombing, said he was glad Dzhokhar had survived.
"I didn't want to lose more than one friend,'' Marvin Salazar said.
"Why Jahar?'' he asked, using Tsarnaev's nickname. "I want to know answers. That's the most important thing. And I think I speak for almost all America. Why the Boston Marathon? Why this year? Why Jahar?''
Two years ago, the city of Cambridge awarded Dzhokhar Tsarnaev a $2,500 scholarship. At the time, he was a senior at Cambridge Rindge & Latin School, a highly regarded public school whose alumni include Matt Damon, Ben Affleck and NBA Hall of Famer Patrick Ewing.
Tsarni, the men's uncle, said the brothers traveled here together from Russia. He called his nephews "losers'' and said they had struggled to settle in the U.S. and ended up "thereby just hating everyone.''