An 18-year-old Ohio prom king died just a week before graduation, and as WKYC reports, toxicology results reveal an unlikely culprit in his death: caffeine poisoning.

Logan Stiner of LaGrange had apparently ingested caffeine powder and died after suffering an irregular heartbeat and seizures. The top student and star wrestler had gone home for lunch on May 27; his brother later found him on the floor, reports ABC 10.

It’s not clear why Stiner took the powder, but his mother later found bags of it in the house. She tells the Chronicle Telegram her son once told her he took some sort of “pre-workout” substance.

Caffeine powder, it’s worth noting, is extremely potent: While an energy drink or cup of coffee typically contains 260 to 280 milligrams of caffeine, a teaspoon of caffeine powder can contain 1,600 milligrams.

Though it’s unclear how much of the powder Stiner ingested, the county coroner notes that 50 micrograms of caffeine per milliliter of blood is regarded as a lethal dose; a milliliter of Stiner’s blood contained 70 micrograms.

(An Arizona mom says energy drinks are to blame for her 16-year-old daughter’s death while on vacation.)

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