Horst and Luisa Ferrero took their intelligent, healthy and happy 3-year-old, Sebastian, in for a medical exam last October. Two days later he was dead, killed by a series of medical errors that began with a massive drug overdose. They have formed the Sebastian Ferrero Foundation in the hopes of preventing similar accidents, and hope to help build a $300 million, 125-bed standalone children's hospital in Gainesville within five years.