How hard would it be to prove Chapel Hill killings were a hate crime?

RALEIGH, N.C. -- The Organization of Islamic Cooperation, an organization representing dozens of Muslim countries, said Saturday the killings of three young Muslims in Chapel Hill, North Carolina, this week "bear the symptoms of a hate crime." But proving religious hate may be difficult in this case.

The murders have made North Carolina a focal point for a worldwide debate over questions of religious intolerance and cultural bias. More than two million tweets have already declared the killings a hate crime.

Namee Barakat's son, Deah, was one of the victims. When asked if he thinks it was a hate crime, he said "absolutely, no doubt about it."

Deah Barakat, his wife Yusor -- who also wanted to become a dentist -- and her little sister Razan, a student at NC State, were killed on Tuesday.

Their neighbor, Craig Stephen Hicks, who had an arsenal of weapons in his condominium, has been charged with the killing.

A global outcry began after police announced the motive for the shooting was a dispute over a parking space. But police and federal investigators say they have not ruled out the possibility of a hate crime.

"It's very hard" to prove a hate crime, according to Joseph Kennedy, a law professor at the University of North Carolina. "It's always hard to get into someone's head. It's always hard to prove motive."

Kennedy said prosecutors will have to prove the main reason the students were killed was because of their race, religion or another protected status.

"It's not enough if it's one of the reasons. It has to be the main reason why they committed the crime," Kennedy said. "You can't prosecute someone for a hate crime simply because of past hate speech or even because of membership in a hate group."

North Carolina does not have a felony hate crime charge, though it is a death penalty state. Prosecutors may be able to make a case for the death penalty even without establishing a hate crime occurred.

Still, leaders at a Raleigh mosque hope to meet with federal investigators next week to make their case. They say it's important to them to prevent other Muslims from becoming victims of similar crimes.