When I first read a story about this, I believe on CNN, ISIS hadn't taken credit, but apparently they now have. This story is a little more recent, and therefore somewhat more fleshed out than the initial post about the incident. Apparently he was an atheist, or at least ISIS believed him to be an atheist. This group is not going away, and apparently it is targeting bloggers in Bangladesh, much in the way that the Mexican drug cartels target journalists and bloggers who post about their crimes. http://www.reuters.com/article/us-bangladesh-attacks-idUSKCN0XK038