CHICAGO (CBS) — Former Thornwood High School basketball standout Chelby Frazier has died.

The cause of his death was not immediately known, according to the Cook County Medical Examiner’s office.

Frazier, 21, starred at Thornwood and was preparing for his senior year season at Robert Morris University.

In a statement, Robert Morris President Mablene Krueger said:

“We at Robert Morris University Illinois were shocked and saddened to learn of the passing of Chelby Frazier. He was a wonderful student athlete poised to begin his senior year. We were looking forward to seeing him complete his college basketball career this season and receive his undergraduate degree.”

Chicago Sun-Times Prep Editor Michael O’Brien reported on Twitter that Frazier may have suffered a seizure while playing basketball.

According to the medical examiner, the location of Frazier’s death was Thornton Township High School, 15001 Broadway in Harvey.

Frazier, a 6-foot, 1-inch guard, averaged 14 points a game for the Eagles last season.