Former Dallas Cowboys and Chicago Bears running back Marion Barber III has died at age 38, the Cowboys said in a statement.

"We are heartbroken by the tragic death of Marion Barber III," the team said. "Marion was an old-school, hard-nosed football player who ran with the will to win every down. He had a passion for the game and love for his coaches and teammates. Our hearts go out to Marion's family and friends during this difficult time."

The cause of Barber's death is unknown.