A the time of Imam Ai (A) the terms Shia and Sunni were not in general use. Even so, these men were not followers of Ahlul bayt (A),
Shimr was a mercenary who fought in one of the regiments of Imam Ali (A) in Siffin, but against Imam al-Husain (A) in Taff
Ibn Muljim was a Kharijite.
The argument that Shias killed Imam al-Husain is spurious; it is contrary to historical evidence and clearly a part of Umayyad propaganda.