CHICAGO (CBS/AP) — An autopsy has determined a former Chicago prep basketball star who collapsed while playing an NBA G League game last weekend suffered a “sudden cardiac death.”

Zeke Upshaw, a swingman for the Detroit Pistons’ G League affiliate, the Grand Rapids Drive, collapsed with about 40 seconds left in Saturday’s game against the Long Island Nets.

Kent County medical Dr. Stephen Cohle told WOOD-TV Upshaw suffered a “sudden cardiac death.” Cohle conducted an autopsy Tuesday, though the investigation will continue for a few weeks.

Cohle said he observed some “cardiac abnormalities,” and he’s working to determine the exact type of heart disease.

Upshaw, 26, grew up in the Hyde Park neighborhood, played high school basketball at the University of Chicago Laboratory Schools, where he was one of the school’s first players to earn a Division I basketball scholarship, when he went to play for the Illinois State Maroons.

After three years at ISU, he transferred to Hofstra for his senior year, where he averaged 19.9 points per game for the 2013-14 season.

Upshaw went undrafted after finishing his college career at Hofstra, and played internationally in Slovenia and Luxembourg. He spent most of the last two seasons with the Drive, appearing in 75 games primarily as a reserve and averaging 7.6 points.