Complex sentence: Cuomo said that, while there was no ongoing threat, he would deploy 1,000 additional National Guard troopers and State Police officers to major commuter hubs during the United Nations General Assembly meeting which began when the bombings were unfolding.
Split into simpler sentences: Cuomo said that, while there was no ongoing threat to the city, he would deploy 1,000 National Guard troopers and State Police officers to major commuter hubs in the city. Security was heightened during the meeting of the United Nations General Assembly which began when the bombings were unfolding.