Translation of this recent question and answer from the Facebook page of Imam Ahmed Alhasan احمد الحسن:
Q: ابو احمد الانصاريOur beloved Master: These days, the opponents of the family of Muhammad℗ are constantly giving the impression (to the Shia) that the ones who killed Al-Hussain℗ are Shia themselves since the leaders [of the Yazidi army that killed him] were close to both Ali and Al-Hassan℗. The opposers of the family of Muhammad℗ implicitly detach the Iranians from the Shia creed, and say that the attack on the Sunnis is from the Persians. Of course, they (the Sunnis) are directing this issue to the demonstrators!*
The question is: Who were the killers of Imam Al-Hussein℗? What was their stance before Al-Taff [the land where Al Hussein℗ was killed], and are they hypocrites whose roots extend back to the Saqifa?**
A: [from Imam Ahmed Alhasan احمد الحسن]: ابو احمد الانصاري(Abu Ahmed Al-Ansari) May God welcome you, my beloved. As for the killers of Al-Hussein℗ and knowing their creed, ideology, or motive for killing Al-Hussein℗, no sane person who thinks rationally or logically says that the killers or some of the killers of Al-Hussein℗ were from the followers (Shia) of Al-Hussein, nor would they say that those who fought with and supported Al-Hussein℗ were from the followers (Shia) of Yazid, the Caliphate line that is supported by the beloved ones of the disagreeing Sunni sect.
This is the issue: Those who fought with Al-Hussein℗—only a few dozen in number—are followers (Shia) of Al-Hussein℗. On the other hand, those who fought Al-Hussein℗ and killed him number in the thousands. They are the followers (Shia) of Yazid and the followers (Shia) of the Caliphate line that the Sunni people support. This is a reality that no one can gloss over or deny.
Regarding the fact that some of those who fought Al-Hussein℗ had sent letters to Al-Hussain and claimed that they would support him if he came to his grandfather Abraham’s land (Iraq), and then betrayed Al-Hussein℗ and joined the army of Yazid (may God curse him), I do not believe that discussing or proving that they were or were not from the followers (Shia) of Ahl al-Bayt℗ before they fought and killed Al-Hussein makes any difference.
The clear truth is that on the tenth of Muharram they were not from the Shia (followers) of the Ahl al-Bayt. Rather, they were from the Shia (followers) of Yazid, the followers of the line of the fallible Caliphate rule and their supporters.
Note: Those who wrote to Al-Hussein℗ asking for his presence and then killed him are small in number compared to the majority Umayyad army who besieged and killed Al-Hussain℗.
*The demonstrators are the Iraqi people who are demonstrating against the political parties.
**The Saqeefa is a roofed building where the people gathered to appoint a Caliph themselves.