Some are referencing 20-year-old brothers Khaled and Saleh al-Oraini as "the most evil twins of the Islamic world" after they stabbed their mother, father and older brother for refusing to join ISIS. The twins were arrested by Saudi authorities in Riyadh after their 67-year-old mother, Haila, died of her severe wounds.

The 73-year-old father and 22-year-old brother are treated at a local hospital, reports The Daily Wire. They remain in serious condition.

Haila reportedly had attempted to stop the brothers from joining the Islamic State in Syria. "Had this come from drug addicts or ignorant youth, it would not have been unusual," a Saudi writer familiar with the case told Reuters. "The shock is that it came from a pair of religious children acting in the name of Islam."

This matricide came as the cleanup process is beginning to rebuild structures destroyed by a coordinated ISIS suicide bomb attack over the weekend. Late Sunday, ISIS militants struck Medina, Jeddah, and Qatif during the Ramadan celebrations. While Saudi police ultimately foiled the attacks and prevented major civilian casualties, the attacks underlined ISIS' willingness to strike even the most devout Islamic societies in the world, reports The Daily Wire.

The Islamic State follows many of the same ideological forebears as the government-sanctioned clerics of the Saudi Kingdom. Although ISIS opposes Saudi Arabia's existence as a monarchy, the group shares many of the same Wahabist beliefs as the puritanical House of Saud.

Some scholars speculate that the teachings of Ibn Taymiyya, a 13th century Islamic scholar from Damascus known for his fatwas (religious opinion) about takfir, were behind young militants killing family members they regarded as apostates.

Islamic State embraces the concept of takfir, often quoting Taymiyya to exhort its followers to kill other Muslims seen as apostates, including relatives. The word takfir is derived from the Arabic word kafer, which means unbeliever.

This isn't the first time devoutly religious Muslim children slaughtered their parents "in pursuit of a higher calling from ISIS." In January, an ISIS militant brutally murdered his own mother in Raqqa, the Syrian capital of the Islamic State, after she attempted to pull him away from the terrorist group.