Note: Fadha Ghozlani shows a portrait of her brother Sayed, who was killed by Islamic State militants in their family house. Among Sayed’s attackers was a cousin.

Sayed Ghozlani was visiting his family during a break from the army, and the fighters wanted to find him. They stormed his house during dinner and corralled the men. They beat them up, tied their hands behind their backs and forced them all to kneel.

Then one fighter pressed a gun against Sayed’s head and demanded his name.

“Abdul Malik,” he replied.

“That’s not the truth,” another militant said in a voice that was familiar, according to two witnesses.

His face bloodied, Sayed looked up to see a figure carrying an AK-47 rifle and smiling triumphantly.

It was his cousin, Muntasir.

In the mountains of western Tunisia, radical Islamists are spreading their ideology, cowing villagers with brute violence and dividing families. American-trained Tunisian soldiers are battling them, but the militants are formidable opponents.