Members of the Albu Nimr tribe fought for months to keep the Islamic State from entering their area, near the Anbar Province town of Hit, about 90 miles west of Baghdad, according to tribal leaders.

But with no support coming from outside, resupply was difficult, and tribal fighters and police officers were badly outgunned by the Islamic State, which captured many heavy weapons from armories in Syria and Iraq. The jihadists finally conquered Hit this month, and have since expanded their control of nearby areas…

More than 40 members of the Albu Nimr were lined up and executed with gunshots to the head in Hit on Wednesday alone, according to Naem al-Gaood, a tribal sheikh related to Jalal al-Gaood.

In a photo circulated online by Islamic State supporters and said to show the aftermath, dead bodies with deep head wounds lie in line, slumped on a curb.