Screen shot of the video

Azat Rozahong taught his sons, one five, the other six, to fire a gun and can be seen in a documentary filmed by the boys' mother.

Their youngest child, a one–year-old daughter, was startled and cried out but no one paid any attention.

The six-year-old pulled the trigger with help from his father. The clip, filmed at a terrorist training camp near China's border with Afghanistan and Pakistan, showed the bullet hitting a tree.

"I didn't feel a thing at the time. When I look back now, it's painful to see my children suffering," Azat said in the documentary. He and his wife are now being held at a detention center in Xinjiang.

His wife hated their life abroad and worries about her children. Watching pigeons is their only entertainment and they keep crying. Her daughter has experienced repeated seizures due to a lack of nutrition.

The youngsters' education and future prospects are dim. Her eldest son can only sing one song, about holy war, and the cartoons they read are full of killing.