In this recent post Professor Juan Cole, Director of the Center for Middle Eastern and North African Studies at The University of Michigan, analyzes the video interviews of the Tsarnaev brothers' aunt and uncle -- Maret and Ruslan -- and gleans something I haven't heard before.
He thinks that from what Maret said it is possible that the brothers' father, Anzor,
was a soldier or security policeman for the pro-Russian Chechnyan government of Akhmet Kadyrov, established in 1999 in the course of the Second Chechnya War against the Islamic Peacekeeping Army, which had invaded Daghestan.
Further,
Maret Tsarnaev seemed to me to say that the father of the two, Anzor Tsarnaev, had worked as an ‘enforcer’ for the Russian authorities, I take it as a policeman or security official. That was the reason, she said, that he had to flee to Kyrgyzstan. That is, far from being rooted in the Muslim fundamentalist wing of the Chechnya rebellion, as many are assuming, the family appears to have been part of the Russian Kadyrov-Putin establishment and opposed to religious radicalism there.
If I recall correctly, the father, Anzor, lives in Russia now, though I don't know when he returned, and that the elder son, Tamerlan, travelled recently to Russia to visit him.
Without just quoting the whole post, the gist is that the brothers felt they "failed' their father - remember the uncle Ruslan repeating "they are LOSERS" in his statement - and this was their means of proving their mettle and getting back at their father.
You really should read Cole's whole post. It's a pretty nuanced and covers many points, including the secularism of ex-Soviet Muslims; the family's emigration, first to Kyrgyzstan and eventually the U.S., where he was "easily" given asylum; and reasons for the sons' possible resentment towards their father, both personally and for his possible complicity in the suppression of Chechen Muslims. As such it doesn't fit in neatly with any of the scaremongering scenarios we're seeing on TV right now, so it's sure to be ignored. But it's a very interesting take.