How did Israel kill Hezbollah chief Nasrallah as part of Operation New Order?

Israel killed Hezbollah chief Hassan Nasrallah in an operation reportedly codenamed 'New Order'. The operation began with a military strike on Hezbollah headquarters in Beirut, which caused destruction of multiple high-rise buildings. It involved two rounds of airstrikes. The underground headquarters were attacked while Hezbollah leaders were coordinating terrorist activities.