Yep other sites reporting that says he is a Muslim convert Rut roh
The internet is a great importer of ideas. If some jackass wants to act out his lunacy and attribute it to one god or another, what's to stop them? There are two levels of support. Material / logistical, and ideological. Maybe a number of people (ISIS, etc) would love to praise him for what he did, but I doubt he had any physical support from them or any other Muslim. Thus, the crime should not be attributed to anyone else. His evil rests with him and him alone.
Having said that, it'd be best if we could learn what connections there could be. Even if not direct support, learning where any ideological support was derived is also useful. If someone is convincing the weak and vulnerable to go commit massacres, that's something we need to know and address.