James Stringer, the father of the late Vikings lineman Korey Stringer, has died, his family said. He was 57. James Stringer died of a heart attack Sunday at the Cleveland Clinic. He had been in the hospital since April because of illness, son Kevin Stringer said. Korey Stringer, a Warren native who played college football at Ohio State, died from heatstroke during 2001 training camp with the Vikings.