How could #1 be true? All ISIS members aren't Muslims and also sunnis are who follow correctly. You think killing muslims, non-muslims and making mischief in the lands are Sunnis? I don't think so.
Do you have any proof for this? As far as I know, there isn't a single non-Muslim member in the ISIS. Also, I don't think there are any Shias or Ismailis with them.
What if I ask you same question? I know the answer will be medias tell they are muslims and some members claim they are muslims. But does that mean all are muslims?
Sunnis are the ones who follow Qur'an and Hadiths correctly. Therefore, how could a person killing muslims, non-muslims and making mischief in lands a sunni/Muslim?