Sociopaths or psychopaths are not easily understood. Mix in some weird ultra dogmatic religious beliefs, add hatred for those who do not do as that socio/psychopath wishes, and filter that through a warped or miseducated mind that is not by any stretch of the imagination matured, and you get in this case what appears to be Islamist extremists who wish to blow the hell out of innocents. Even Bill Mahrer
http://www.youtube.com/watch?feature=player_embedded&v=4YG_mqZJKcM , as addled as he usually is, gets this much. Not all religions are the same. Not all people who are strict adherents to their religions are the same. But if a person is a strict believer in certain ultra violent facets of what some say is a deadly perversion of a radicalized Islamist belief, then you get folks killing folks in the name of religion.
People try to dance around the obvious way too much these days. Afraid they might accidentally offend, they parse words and use phony PC speak. I have less use for these wussified morons than I used to years ago, and then I was not exactly the patient type. There is evil in the world, there is good in the world. What these 2 guys in Boston did was pure evil. Other parts of the world deal with this stuff on an almost daily basis. Here in the US we do not, it is the exception.
Prayers for the families and for the victims of this horrific act.