Is it true that he will be martyred at the hands of a bearded old woman? How does such a crime take place despite the Imam's uprooting of oppression?

There are various narrations about Imam Mahdi's martyrdom or demise; and as this event is due in the future, obviously the only way of unveiling the mysteries surrounding it is by studying the narrations related from the Infallibles in this regard. Nevertheless, the narration pertaining to the event of Imam Mahdi being murdered by an old woman is not accepted as authentic by most scholars. This story has only been recorded in Ilzām al-Nāsib and lacks authentic narration. However, if we do accept this narration, it must be noted that what is for certain is that the universal rule under Imam Mahdi will be the rule of justice and equity, and as such the rule of the oppressors will be destroyed. However, this does not necessarily certify that there will be no possibility of individuals sinning.