An Ohio teenager who collapsed just days before his graduation died of a caffeine overdose, according to an autopsy.

Logan Stiner, 18, was found dead on the floor of his home in LaGrange around 11 a.m. on May 27, News Net 5 reports.

Stiner’s brother found him lying on the floor.

“He’s on the ground passed out. I don’t know how long he’s been lying here,” the brother said in a 911 call.

At first, authorities believed Stiner's death was because of natural causes, the Chronicle Telegram initially reported.

That same day, his mother, Katie Stiner, found bags of caffeine powder in the house. It took an autopsy to connect the powder to Stiner's death, according to the Chronicle Telegram.

Lorain County Coroner Dr. Stephen Evans said Stiner was found with more than 70 micrograms of caffeine per milliliter of blood in his system -- 20 micrograms more than what is considered a lethal dose.

It is unclear why Stiner was taking the caffeine powder, but he was a successful high school wrestler and once told his mother he took some sort of "pre-workout" substance, Newser reports.