A spokesperson for the Los Angeles County coroner's office said their investigation will be complete in "about a week" and that Peterson's body was still being held at their office.
Peterson took over the training of Seattle Slew in 1978 from Billy Turner, who was fired by owners Karen and Mickey Taylor and Sally and Jim Hill. In Peterson's care, Seattle Slew won the Marlboro Cup (gr. I), Woodward Stakes (gr. I), and Stuyvesant Handicap (gr. III), and also finished second by a nose to Exceller in the Jockey Club Gold Cup (gr. I). That year, Seattle Slew won five of seven starts overall and earned $473,006.In addition to Seattle Slew, Peterson also trained multiple stakes winner Sigfreto and Apalachee Ridge, who set the six furlong track record of 1:07 2/5 at Hollywood Park in 1997. He was also well known as one of the Southern California circuit's top claiming trainers.Peterson is survived by one son, David. Funeral arrangements are pending.