The attackers had disguised themselves as IRGC soldiers and Basij volunteers, blending into the crowd before taking positions in a park overlooking the parade route. They targeted both the marching soldiers and a viewing stand filled with civilians. The shooting lasted roughly ten minutes. When it ended, the boulevard was chaos -- wounded carried to hospitals, contradictory reports already flooding Iranian state media. Initial accounts said four attackers were killed on the spot; later reports identified a fifth, initially mistaken for a victim. The death toll itself remained contested: Iranian sources reported 25 dead, while CNN put the number at 29. Among the dead were a four-year-old boy and several young conscripts.

Within hours, two groups claimed responsibility, and the confusion only deepened from there. The Arab Struggle Movement for the Liberation of Ahwaz, an Arab separatist group, initially took credit through their spokesperson on Iran International TV, calling it a response to "the establishment's tyranny against Ahvazis." Then the Islamic State released a video through its Amaq news agency purporting to show the attackers. The following day, ASMLA reversed course, posting a statement on its website denying involvement and attributing the original claim to a splinter faction expelled from the organization in 2015. By September 26, ISIL's official spokesman released an audio message formally claiming the attack. The competing narratives left a muddled picture that various governments would interpret to suit their own agendas.

The funerals on September 24 drew thousands to Ahvaz's Sarallah Hussainiya. Mourners waved Iranian flags and carried photographs of the dead. ABC News described the scene as "a collective outpouring of grief." But grief quickly became geopolitics. Supreme Leader Ali Khamenei accused Saudi Arabia and the United Arab Emirates of financing the attack, calling them "puppets of the United States." Iran summoned the ambassadors of Denmark and the Netherlands for hosting ASMLA members. General Hossein Salami of the Revolutionary Guard labeled Saudi Arabia, Israel, and the United States the "evil triangle" and vowed revenge. All three countries denied involvement. The U.S. defense secretary called the allegations "ludicrous."

The attack exposed tensions that run deep in Khuzestan. Ahvaz sits on the Karun River, Iran's only navigable waterway, in a province that holds much of the country's oil wealth yet whose Arab minority has long complained of marginalization. The city was heavily bombed during the Iran-Iraq War and bears the scars of that conflict in its infrastructure and its memory. Sacred Defence Week exists precisely because Khuzestan was the war's primary battleground. That the attack occurred during this specific commemoration, in this specific city, added layers of meaning that extended far beyond the immediate violence. In the aftermath, 22 suspects were arrested. Iran fired missiles at targets in eastern Syria, claiming to strike ISIL leaders responsible for the attack. The United Nations Security Council condemned the assault and called for the perpetrators to be brought to justice.