The September 29 Attacks were an attack on E-Corp buildings housing documents meant to help rebuild their financial database. The attack caused 71 buildings across the country to explode or catch fire and left over 3000 people dead. The official story is that the attack was perpetrated by Sunil Markesh and Shama Biswas on behalf of Iran, however the Dark Army and Tyrell Wellick are the true culprits.
Originally the attack was supposed to only target one building in New York City, but due to Elliot Alderson rerouting the paper records, Tyrell Wellick and the Dark Army had to change the plan.