Former Dallas Cowboys running back Marion Barber III has died at the age of 38, the team announced Wednesday.
"We are heartbroken by the tragic death of Marion Barber III," the Cowboys said in a statement. "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 not currently known.
"Frisco Police responded to a welfare concern at an apartment believed to be leased by Marion Barber," the Frisco police department said in a statement. "Frisco Police along with the Collin County Medical Examiner's Office are investigating an unattended death at the location."
Barber played in the NFL from 2005 to 2011, spending his first six years with the Cowboys, who selected him in the fourth round of the 2005 draft out of the University of Minnesota.
Barber's best season in the NFL came in 2007 when he rushed for 975 yards and 10 touchdowns while adding two more scores through the air en route to Pro Bowl honors.
Following the 2010 season, Barber signed with the Bears and spent his final season in Chicago before announcing his retirement in March 2012.
"We are saddened to learn of the passing of former Bears RB Marion Barber III. Our hearts go out to his family and friends," the Bears said in a statement Wednesday.
Barber played under Pro Football Hall of Fame coach Bill Parcells to start his career. Parcells had the highest of praise for his former running back.
"I hold him in high regard," Parcells told the Dallas Morning News. "I hate to bring up football now because that's not important, but he was almost like a perfect player. In this respect, he could run, block, he could catch, he was tough and he was always there."
Over his seven years in the league, Barber totaled 4,780 yards and 53 touchdowns rushing, and 1,330 yards and six touchdowns receiving.