I want to know how Dzhokhar Tsarnaev went from popular, easy going high school student

[JDPriestly]

32. What if the motivation was revenge for the insult to the family's honor

when his mother was arrested?

For a Chechen a guest is a sacred person. That’s why friendship is appreciated so highly, as well as helping the weak person or those in need. A story tells about a driver who accidentally knocked down a woman on the street, and she died immediately. The driver took her in his arms and rushed to the nearest house, praying to God for help and mercy, for he had neither relatives nor friends near by. The man who opened the door saw his dead mother, and said to the praying driver: "Keep calm, I’ve heard your prayer. This dead woman an is my mother, and if you wish, I’ll be your brother from this day on. But by God, if you had only left her at the road and tried to run away, I would spend all my life looking for you in revenge for my mother."

http://www.truth-and-justice.info/chechnat.html

That appears to be some sort of pro-Chechen website. I have heard about this kind of revenge culture in that area before.

Here is a reference to that revenge culture in a footnote in what may be a scholarly publication.

Chechnya at a Turning Point
Winter/Spring 2001 – Volume VIII, Issue 1

Notes
. . . .
2. Blood revenge remains an essential component of Chechen culture. The filtration camps were used to hold numerous Chechens in temporary custody, officially in order to determine what links, if any, they might have with the rebels. The detainees were badly beaten and tortured.

http://www.watsoninstitute.org/bjwa/archive/8.1/Chechnya/Shenfield.pdf

Here is a link to the Watson Institute's website:

http://www.watsoninstitute.org/