REPORT: Dzhokhar Tsarnaev note found in boat points to mystifying motive we may never truly understand. ““Basically the note says that he does not mourn his brother Tamerlan, that Tamerlan was a martyr now and that he was in paradise, that Dzhokhar expected to join him there soon,” . . . . That the bombings were in retribution for the US crimes against Muslims in places like Iraq and Afghanistan; that the victims of the Boston bombing were ‘collateral damage,’ the same way innocent victims have been collateral damage in US wars around the world, summing up that when you attack one Muslim, you attack all Muslims.”

So, probably just teen alienation then.