The Iranian capital was quiet at night after the July 30 inauguration of President Masoud Pezeshkian, which brought scores of foreign delegations to Tehran. But at 1:45 am local time, shocked residents in the affluent north of the city reported the sound of a loud explosion. Within hours, Iranian authorities confirmed that Ismail Haniyeh, the visiting leader of the Palestinian Hamas movement’s political bureau, had been assassinated. A regular visitor in recent years, Haniyeh was in Tehran to attend the inauguration of Pezeshkian.

Details of the incident in the public realm remain scant. According to an initial statement released by Iran’s Islamic Revolutionary Guard Corps (IRGC) at 6:10 am local time, Haniyeh’s "residence” was struck, resulting in the...