Gupta: 9/11 then and now

Editor's note: Dr. Sanjay Gupta investigates 9/11's toxic dust – what it felt like to breathe it, be enveloped by it, and what the experience means for the next time disaster strikes, in "Terror in the Dust," Saturday, 9 p.m. ET. I still remember the patient I was examining on the morning of September 11, [...]