Who killed Uthman? Were his killers leaders in the army of Ali ibn Abi Talib? And what was Ali's stance on Uthman's killing?

The two men who killed Caliph Uthman, may Allah be pleased with him, were from Egypt. Muhammad ibn Abi Bakr guided them to him. They entered upon him from a house next to his. His wife said to Ali: "I do not know, two men whom I do not recognize, along with Muhammad ibn Abi Bakr, entered upon him." Ali then summoned Muhammad and questioned him. He said: "She did not lie. By God, I did enter upon him, and my father reminded me, so I left him, and I am repentant to Allah Almighty. By God, I did not kill him nor did I restrain him." His wife said: "He spoke the truth, but he let them in." It was also said: "The one who took charge of killing him was a man from Egypt, blue-eyed and fair-haired, called Himar." They were not commanders of Ali's army. Ali and other Companions had sent their sons and freed slaves to protect him. Ali, may Allah be pleased with him, intended to exact retribution from the killers once matters had settled, but the tribulation continued until he was martyred, may Allah be pleased with him.