An American Christian teacher in northern Iraq was murdered Thursday by one of his Muslim students.

Authorities say the 18-year-old Biyar Sarwar shot gym teacher Jeremiah Small and then killed himself at a Christian school in Kurdistan. It's not clear if religion was a motive.

Small's students said the teen gunman frequently talked about Jesus Christ and prayed in class.

"I'll never forget these cruel moments," said Kamal, who was in the classroom at the time of the shooting. "I have no idea what the motive was - both were good people."

Servant Group International, a Tennessee-based group, commissioned the 33-year-old Washington state native to go to Iraq.

"We believe this is an isolated incident, just like (what) happens in the U.S.," Jeff Dokkestul, a Servant Group International board member, told The Associated Press.

Friends say Small wanted to go to share the gospel with Muslims.