Complex sentence: Stottlemeyer explains that Burnshaw used to head the FBI's field office in Atlanta until the Centennial Olympic Park bombing during the 1996 Summer Olympics, when he'd accused the wrong guy on network television, an instant career killer for him.
Split into simpler sentences: Stottlemeyer explains that Burnshaw used to be a real player, and was the head of the FBI's field office in Atlanta until the Centennial Olympic Park bombing during the 1996 Summer Olympics. He'd accused the wrong guy on network television, an instant career killer for him.