Ayman al-Zawahiri, the man who replaced Usama bin Laden as the head of Al Qaeda, has reportedly declared war on ISIS “caliph” Abu Bakr al-Baghdadi in a newly released audio message.

In the message, which was released on Wednesday, al-Zawahiri calls the Islamic State illegitimate and insists that al-Baghdadi is not the leader of all Muslims.

Rob O'Neill, the man who killed bin Laden, told Greta Van Susteren tonight that the Al Qaeda-ISIS rift is unusual since both groups follow Salafi Sunni Islam and share similar goals.

O'Neill explained that ISIS, formerly the Al Qaeda branch in Iraq, split from the larger group two years ago. Since then, ISIS has grown exponentially in Iraq and Syria.

O'Neill suggested that Al Qaeda may have declared war on ISIS because they're looking for publicity and additional funding from places like Saudi Arabia.

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