Authorities say a 16-year-old boy has died after attending the Lollapalooza music festival in Chicago.

Police and the medical examiner’s office identified the teen as Evan Kitzmiller. He was found unresponsive Sunday night, the last day of the weekend festival, and pronounced dead at a hospital.

Investigators didn’t release details about his death. But Kitzmiller’s mother says her son had a seizure and his heart stopped.