Khalifa Uthman bin Affan - Ubaidullah's orgy of murder

Assassination of Umar, a conspiracy?
When Umar was stabbed by a Persian slave Firoz, a question arose whether this was the act of a single disgruntled person or whether it was the result of a conspiracy. Abdur Rahman b Abu Bakr reported that the previous day, he had seen Firoz, Jafina and 1-lurmuzan conferring together. Seeing him the three men were confused, and a double edged dagger fell from the hands of one of them. It was alleged that that was the dagger with which Umar had been stabbed.

When Ubaidullah a son of Umar heard the report of Abdur Rahman, he took his sword, and rushed out of his house to take the revenge for the assassination of his father. After stabbing Umar, Firoz had killed himself. Ubaidullah first went to the house of Firoz, and killed his wife and daughter. He then sought Jafina. He was a Christian of Hirah, who had been brought to Madina after the conquest of Iraq. He was employed in teaching the art of writing to the Arab students. Ubaidullah killed Jafina. Thereafter Ubaidullah went to Hurmuzan and killed him likewise. Hurmrzan was a Persian General who had been taken captive in one of the Persian campaigns. He accepted Islam and settled in Madina. Umar had sanctioned a stipend for him. When the Muslims came to know that in a fit of frenzy, Ubaidullah had killed four persons, they apprehended him and confined him to his house.