Who was Ismail Haniyeh, the Hamas political leader who was killed in Iran?

Haniyeh was dismissed after a year in office by Palestinian President Mahmoud Abbas after Al-Qassam Brigades, the military wing of Hamas, took control of the security services centers in Gaza. Haniyeh rejected the decision because he considered it "unconstitutional" and described it as hasty, stressing that "his government will continue its duties and will not abandon its national responsibilities towards the Palestinian people."