Via Newsweek:

U.S. officials increasingly believe that the military unit ambushed by an Islamic State militant group (ISIS) affiliate in Niger was attacked as the result of being set up by people in a village sympathetic to local jihadis.

Details about the October 4 attack that left four U.S. soldiers—all Green Berets—dead are only now being revealed.

The militants were likely tipped off by at least one accomplice who may have lived within the local population, U.S. officials briefed on the case told NBC News. Almou Hassane, the mayor of the village in question, Tongo Tongo, told Voice of America that “the attackers, the bandits, the terrorists have never lacked accomplices among local populations.”

Nigerien authorities have detained the chief of the village, Mounkaila Alassane, adding to the suspicion that the dozens of ISIS-affiliated militants who attacked the unit had prior information about the soldiers’ movements.

A joint U.S. and Nigerien patrol spent the evening near the Malian border before the attack. Local reports indicate that the purpose of their mission may have been to locate an associate of Abu Adnan al-Sahraoui, a member of the Islamic State in the Greater Sahara, or ISGS, the affiliate suspected of the ambush.

“They must have spent the night in the northwest of Tongo Tongo,” Hassane said.

The soldiers met with elders of the village, which they knew was likely sympathetic toward ISIS, and officials told NBC News that villagers made efforts to delay the Green Berets’ departure.

When the soldiers left the village in unarmored vehicles, dozens of jihadis launched a sneak attack with machine-gun fire and then mortars and rocket-propelled grenades. The soldiers exited their vehicles and started to fire back, but were outnumbered and outgunned. They tried to retreat but were ambushed again a mile away.