NEW: An armed security guard is being hailed as a hero after stopping a gunman who fatally shot a woman and opened fire inside a cafeteria at a massive Citibank

NEW: An armed security guard is being hailed as a hero after stopping a gunman who fatally shot a woman and opened fire inside a cafeteria at a massive Citibank campus in Tampa, Florida. Authorities say the suspect crashed through a fence into an outdoor seating area filled with people eating lunch…