Look, this is terrible, absoloutley, but you should not be surprised by what ISIS are prepared to do.
Al qaeda and the Taliban have distanced themselves from ISIS, that says a lot. ISIS are essentially the nazis of their day, they aren't just fighting for territory like Palestine/Israel, they aren't about revenge for western interferance in what ever country like Al qaeda/Taliban. They literally just want to convert the every nation on earth to an extremist Islamic state.
It's pretty ****ing dumb because we're in 2014 not the 13th century, you can't just do a Genhis Khan and take over the world 1 village at a time. Interested to know how they plan to conquer and assume power in nations like the UK, US and China. Terrorist attacks and guerilla warfare with AK-47s is one thing, overthrowing a wester super power is just fantasy.
(I don't know every last thing about ISIS or their ideologies, this global dominaition crap is just what I've picked up from seeral videos, news articles and TV reports including a tape by a British born ISIS member stating that it's not just the east they want and eventually they will bring Islam and ISIS to Britain and the rest of the world in due time)