Ali Saqr al-Qasem used an assault rifle to execute his mother Lena, 45, after she was found guilty of apostasy.
The London-based Syrian Observatory for Human Rights revealed that Ms al-Qasem was also accused of trying to persuade her son to abandon ISIS and flee Syria with her.
Fearing for his own safety within the brutal organisation, it appears Ali reported his mother, leading to her arrest.
It is likely she was subjected to a trial in the local Islamic court, situated near the roundabout where notorious British jihadi Mohammed Emwazi was killed in an airstrike.
It is unclear why Ali was given the task of executing his own mother. However it is possible he may requested to carry out the harrowing act or more likely he was ordered to do it as a test of loyalty.
ISIS, who over the years took over from Al-Qaeda in vast areas of Iraq and Syria, has gained prominence by establishing a culture of fear and mass violence such as mass shootings and beheadings.
The violent videos of its members executing both locals and westerners is believed to be part of the organization’s sophisticated propaganda campaign.