Fire was the primary cause of the collapse of World Trade Center Building 7 in New York City, according to a federal agency.

He also was involved in such notable projects as a new master plan for the National Mall in Washington, D.C. and an expansion of Dulles International Airport in Virginia.

David Childs, the lead architect of the One World Trade Center skyscraper that rose from the site where the Twin Towers collapsed in New York City during the 9/11 attacks, has died. He was 83.