An incident in California has exposed an interesting division in Islam.

You have undoubtedly heard of Muslims becoming outraged when people show images of Muhammad. Many Muslims, but not all, consider such images as an act of blasphemy.

Maziar Behrooz, who teaches at San Francisco State University, found himself under investigation by school administrators for allegedly showing a picture of Muhammad in one of his classes, Front Page reports.

This is perhaps the most disturbing aspect of this story as it appears by opening an investigation, the university is prepared to enforce Islam’s blasphemy laws in America.

But here is the fascinating twist. Behrooz is a Muslim and teaches Islamic history at the university. But he is also a Shia Muslim and Shiites actually allow and use pictures of Muhammad as part of their religious expression.

However, Sunnis, another branch of Islam do not, and they consider it a blasphemous act to have a picture of Muhammad.

And according to Front Page, Behrooz was allegedly showing a Shiite icon of Muhammad, and it is suspected that a Sunni Muslim made the complaint.

READ: San Fran State Investigates Iranian Islamic Studies Prof for Blasphemy

The difference between Shia and Sunni Muslims

Sunnis make up 85% of the Muslim population and Shia 15%.

The difference between Sunni and Shia Muslims dates back to 632 AD and the death of Muhammad and an argument on who was to lead the Islamic religion.

The Sunni believe that anyone who faithfully follows the Islamic tradition can be chosen to lead Islam, while the Shia hold that the leader must be a direct descendant of Muhammad.

Because their leading Imam is a direct descendant of Muhammad, Shiites also believe he is sinless and often look upon them as saints.

As the dominant branch of Islam, Sunni Muslims are found around the world, while Shia Muslims are relegated to primarily Iran and parts of Iraq.