Clarence Williams, a retired running back for the San Diego Chargers and the Washington Redskins, died Sunday after being shot in his car at an intersection.

Williams, 39, a star at the University of South Carolina in the middle 1970s, died about 4 a.m. at Richland Memorial Hospital, said Margaret Gregory, a spokeswoman for the Richland County Sheriff's Department.Williams was shot in the back about 11:45 p.m. Saturday while he and a friend were at the intersection of McRae and Pearl streets.

Investigators have not identified a suspect or determined a motive, Gregory said. They would not release the name of Williams' friend, who was trying to drive Williams to a hospital for treatment when authorities arrived."What we know is that the shots came from outside the car," Gregory said.

Investigators have not ruled out the possibility of a drive-by shooting, she said.

Williams was a running back for South Carolina from 1974 to 1976. In 1975, he compiled the Gamecocks' fourth best rushing season with 1,073 yards, behind Kevin Long, who ranked third during that season, and first- and second-ranked George Rogers.

Williams ranked ninth in career rushing yardage at South Carolina with 2,311 yards.

His best game was in 1975, when he ran 160 yards to defeat arch rival Clemson, 56-20. The next year, he was the leading rusher with 873 yards.

In 1977, Williams moved to the NFL, playing for the Chargers from 1977 to 1981 and the Redskins in 1982 and 1983.

Jim Carlen coached Williams at South Carolina.

"That year we only had two running backs," he said. "We had redshirted Ron Bass at quarterback, and we played almost all the time with Jeff Grantz (at quarterback), Long and Williams (at running backs).

"He was a tough kid. When I got there, they told me he would not play hurt, but he would," Carlen said. "He was flashy with good quick feet. He's a class guy."

Carlen said that he talked to Williams about six months ago and that Williams had promised him he would go back to school to finish his degree.

"That's shocking," he said of the shooting. "He was a real quiet youngster."