Marion Barber played a final season with Chicago in 2011 after spending his first six years with the Cowboys. He had mental health problems after his career.
Police in the Dallas suburbs of Frisco said Wednesday they had a welfare check on an apartment that was "believed to be leased" by Marion Barbara and were investigating an untimely death there.
The Cowboys, headquartered in Frisco, said they were "heartbroken by the tragic death of Marion Barbara III."
"Marion was an old-school, hard-nosed football player who ran down every one of them with a desire to win," the team said. "He had a passion for the game and a love for his coaches and teammates."