Sports Ex-Cowboys running back Marion Barber III’s death caused by heatstroke, coroner says July 11, 2022July 12, 2022 Tom Schad, USA TODAY Comments Off on Ex-Cowboys running back Marion Barber III’s death caused by heatstroke, coroner says Frisco police have been investigating Marion Barber III's death since the former Cowboys running back was found in a Dallas apartment on June 1.