A kaleidoscope of images, adjectives and anecdotes tumbled forth on Friday to describe Tamerlan Tsarnaev, 26, and Dzhokhar Tsarnaev, 19, the two brothers suspected of carrying out the bombings at the Boston Marathon that killed three people and gravely wounded scores more.

Image Dzhokhar Tsarnaev was an all-star wrestler at Cambridge Rindge and Latin High School.

What no one who knew them could say was why the young men, immigrants of Chechen heritage, would set off bombs among innocent people. The Tsarnaevs came with their family to the United States almost a decade ago from Kyrgyzstan, after living briefly in the Dagestan region of Russia. Tamerlan, who was killed early Friday morning in a shootout with law enforcement officers, was 15 at the time. Dzhokhar, who was in custody Friday evening, was only 8.

In America, they took up lives familiar to every new immigrant, gradually adapting to a new culture, a new language, new schools and new friends.

Dzhokhar, a handsome teenager with a wry yearbook smile, was liked and respected by his classmates at Cambridge Rindge and Latin School, where celebrities like Ben Affleck and Matt Damon had walked the halls before him. A classmate remembered how elated he seemed on the night of the senior prom. Wearing a black tuxedo and a red bow tie, he was with a date among 40 students who met at a private home before the event to have their photos taken, recalled Sierra Schwartz, 20.

“He was happy to be there, and people were happy he was there,” Ms. Schwartz said. “He was accepted and very well liked.”