The FBI knew that legendary slugger Mark McGwire used steroids during his career. McGwire admitted as much on Monday, but retired FBI agent Gary Stejskal uncovered the details of McGwire's doping regimen from informants almost two decades ago. Stejskal, who helped lead the first major federal investigation into illegal steroid distribution called Operation Equine, confirmed that McGwire and his then-Oakland A's teammate, Jose Canseco, were among those identified as steroid users during the probe that ran from 1989 to 1993.