The cause of death of former Dallas Cowboys running back Marion Barber was determined to be an accidental heat stroke, according to a report from the Collin County Medical Examiner’s Office released Monday.

Barber, 38, was found unresponsive in his Frisco Apartment on June 1 by police responding to a welfare check. Police responded to the apartment complex after another tenant reported water was leaking from Barber’s unit. Apartment staff was subsequently unable to contact Barber, and the unit was locked from the inside.

One of the bathtub faucets in Barber’s apartment was running when officers arrived, and the unit’s thermostat was set to 91 degrees with the heat set to “on,” according to the coroner’s report.

Police also found exercise equipment in the unit.

“Mr. Barber was known to exercise in sauna-like conditions,” the coroner wrote in his report.

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Barber’s family members had not heard from him for six days before when his body was found, according to the Frisco Police Department’s incident report. His family also noted that Barber “was known to have a history of medical problems and mental health concerns.”

“We are heartbroken by the tragic death of Marion Barber III,” the Cowboys said in a statement on Twitter after Barber’s death. “Marion was an old-school, hard-nosed football player who ran with the will to win on every down.”

The Cowboys drafted Barber in the fourth round of the 2005 NFL Draft out of the University of Minnesota. He spent six seasons in Dallas, racking up more than 4,000 yards and 47 touchdowns. Barber played for the Chicago Bears for the 2011 season before retiring.

The running back was known for his physical running style, often breaking tackles and churning his legs to pick up extra yards after contact.

Barber’s friend Joe Krywalski told NBC 5 after his death that Barber was a wonderful person who was very charitable, religious, and enjoyed playing the piano.

Billy Clark was Barber’s attorney and more.

“For me, he was literally family and I’m so lost that I’m not prepared for this,” Clark said.

Clark says Barber planned to write a book about his life and what football and family meant to him. Barber was also training to become a boxer.

“He was in tip-top shape so when I tell you I’m at a loss, I am,” Clark said.