Why are ISIS killing Muslims? I thought they were Muslims? What are they?
Majority of their victims have always been Muslims.
They regard most of us as apostates. Anyone who does not give "bay'ah" (pledge of allegiance) to the so called "Ameer al-momineen" (leader of the Muslims) Al-baghdadi is an apostate according to them. Either you're in the camp of the "Muslims" (meaning ISIS) or you're in the camp of the disbelievers (anyone who is not with ISIS). They even regard other jihadist movements as apostates
They even got al Qaeda shook
They also believe that if they cause as much mayhem in the Muslim world as possible, the people will eventually revolt against the "Apostate regimes" and demand an Islamic caliphate.. It's straight from the playbook of Gama'ah Islamiyyah, the extremist group that was formed by Ayman Zawahiri, the current leader of Al Qaeda, in Egypt.