Who are the Killers?

Anyways, who are the killers of Janāb Ḥusayn? Ibn Ziyād, Shimar, and the people of Kūfah are the killers of Janāb Ḥusayn. These people of Kūfah invited him and said they will die but not accept Yazīd as their ruler rather will accept only Janāb Ḥusayn as their ruler, but after calling him, they betrayed and forget their bayʿt, promises, these are the actual killers of Janāb Ḥusayn and even till today these people are mourning, if these people had given their lives at that time instead of mourning now, if they had sacrificed blood at that time instead of sacrificing now, then perhaps Janāb Ḥusayn would have been saved from being martyred unjustly. Much oppression took place, but Janāb Ḥusayn has not been in a loss at all, as Allāh had to rank Janāb Ḥusayn in a very high and esteemed place, so He did.