I've been reading a shit ton of reports on them this morning. So far, it's mainly just more journalist speculating shit so they have something to talk about.
The only thing I've read of any value is that the younger (dead) brother list's his religion as Muslim on a Russian social network, and the older brother said he was Muslim to a school newspaper that interviewed him once.
All the ties to Al Quaida and Muslim extremist talk seems to be internet speculation so far.
And pressure cooker bombs were used by home grown terrorist in the Atlanta summer games bombing, so again, that's not something exclusive to Arabic countries.