(CBS News) The investigation into the Boston Marathon bombings and their perpetrators is moving ahead. Jim Axelrod reports on the suspects:
For those who knew the Tsarnaev brothers, the questions are personal.
When asked who would do something like this?, Larry Aaronson replied, "Not Dzhokhar. Not him."
Aaronson once was a teacher at the high school the younger Tsarnaev brother, Dzhokhar, attended.
"I know this kid to be compassionate, I know this kid to be forthcoming," Aaronson said. "He's a great athlete, he's a sportsman. He's never been in trouble."
The two brothers, who are ethnic Chechens, came to the U.S. with their family a decade ago, escaping the vicious fighting between the Russian government and the separatist, largely-Muslim Chechen rebels.
Dzhokhar, who became an American citizen on September 11 of last year, is 19 years old, a student at the University of Massachusetts Dartmouth.
His older brother, Tamerlan, was 26 years old, married to an American woman, with a young daughter. He studied engineering at Bunker Hill Community College, but dropped out.
Tamerlan was an accomplished boxer -- a New England Golden Gloves heavyweight champion.
Julian Pollard, who roomed with him during a boxing tournament, said, "He was confident in his abilities. He wasn't shy about sharing that."
"Did you have a sense of him? What kind of guy was he? What was he talking about?" asked Axelrod.
"The first year I met him I would describe him, like I said, he was a little flashy, maybe a little arrogant, little cocky, but nothing out loud. His clothing said it more than he did verbally," Pollard said.
"Then the next year I met him at the same tournament and he was just a different guy. The way he carried himself was just more humble. He only spoke about his faith. He was big into religion."
Both brothers were Muslims.
Their uncle, Ruslan Tsarni, says he, too, saw changes in Tamerlan.
"It was different Tamerlan, seeing no purpose in life, but a pursue path of God," Tsarni said. "OK, when I ask, 'What is the path?' he would say, 'Some kind of Jihad.'"
On his YouTube page last year, Tamerlan endorsed several Jihadi videos.
But what about Dzhokhar, the younger brother?