On Aymenn Jawad Al-Tamimi's Blog Suqur al-Furat: A Pro-Assad Sha'itat Tribal Militia Points out members of the Sha'itat tribe joined IS and then participated in punitive massacres of their own kin. Not unusual, that was a common IS highly divisive MO in managing tribes. In Iraq this has often resulted in vengeful parts of Sunni Arab tribes fighting alongside Shia Hashd against IS remnants. Atrocities have been common in such situations. There's sometimes a danger of a cycle long running feuds across kinship networks if blood money isn't paid.