Seems to be dispute that this is either Dan Shanower or a seal team 6 member. He does give hints. He mentions decades which would be 2001. He was a Commander in the Navy at the Pentagon during 9-11

Commander Dan Shanower September 11 Memorial | The City of ...
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Commander Dan Shanower Commander Dan F. Shanower, 40, combined strong patriotism with a taste for adventure and a wonderful sense of humor. A Navy intelligence officer, he had just begun gathering information on the World Trade Center attacks to brief his superiors when the hijacked plane that struck the Pentagon killed him.