OMAHA, Neb. (AP) — An autopsy showed excessive heat was the main factor in an Omaha high school football player’s death during practice in August, the Omaha World-Herald reported.

Douglas County Attorney Don Kleine said that while the autopsy showed the primary cause of death as hyperthermia, it also showed 16-year-old Drake Geiger suffered from heart problems that contributed to his death.

Geiger’s father, Scott Hoffman, had previously told the World-Herald and the autopsy confirmed that the teen was 6-foot-3 and around 400 pounds. He had no known medical conditions prior to his death, his father said.

Geiger had been practicing with the Omaha South football team the afternoon of Aug. 10 when he collapsed. The temperature was 91 degrees with a heat index of 105 at the time Geiger collapsed, and the National Weather Service had issued a heat advisory for the day.

Geiger was one of several high school football players around the country in the weeks before his collapse to die during a practice or conditioning session, according to media reports.