A medical examiner’s report reveals that former Cowboys and Bears running back Marion Barber died of a heat stroke, USA Today reports.

Barber was found unresponsive by police in his Frisco, Texas, apartment on June 1 during a welfare check.

Dallas Cowboys running back Marion Barber signs autographs for fans during training camp in Oxnard, California, on Aug. 14, 2010. (Ron Jenkins/Fort Worth Star-Telegram/Tribune News Service via Getty Images)

According to the medical examiner’s report, the former running back had a habit of exercising in extreme heat. When police entered the apartment, they found the thermostat set to 91 degrees with one of the bathtub faucets turned on. They also observed exercise equipment in the room.

Marion Barber #24 of the Dallas Cowboys runs with the ball against the Carolina Panthers during their game at Bank of America Stadium on December 22, 2007, in Charlotte, North Carolina. (Streeter Lecka/Getty Images)

Barber spent the first six years of his career in Dallas and his seventh and final season in Chicago. The former Golden Gopher totaled 4,780 rushing yards in his career and 53 touchdowns.

Barber was 38 years old.