officer alex castro wears badge number 674 with pride. before him, it was worn by his uncle, jose feliciano. >> it's a constant reminder representation of him, as well as the police diameter. >> reporter: he spent more than two decades with tbd, many of them under cover in high-level, high-stakes drug investigations. >> him and his team were part of a big reason why the drug activity here in tampa started to reduce. >> when you are meeting with high-level drug traffickers on a day-to-day basis, you are doing something that only a unique individual can do. >> reporter: any given day could have been his last. now, years after his retirement, he finds himself dealing with another dangerous foe. this one, he can't fool or talk his way out of. he has been diagnosed with gastric cancer. he is 61 years old. >> he is... at a point in his life right now that it's life or death. >> reporter: his family and friends starting an online fund-raising effort to put him had on a medical flight from his current home, back to tampa for treatment at moffitt