Davis Allen Cripe died in a hospital on April 26 after collapsing in a classroom at Spring Hill High School in Chapin.
On Monday, the Richland County Coroner ruled that he died from a "caffeine-induced cardiac event causing a probable arrhythmia."
"Davis, on this particular day within the two hours prior to his death, had consumed a large diet Mountain Dew, a cafe latte from McDonald's, and also some type of energy drink," coroner Gary Watts said at a press conference.
Watts could not specify which energy drink Cripe consumed.
"It was so much caffeine at the time of his death that it caused arrhythmia," Watts sad, referring to a condition marked by an irregular heartbeat.
Watts told BuzzFeed News that according to eyewitnesses the biggest issue was that Davis "slammed or chugged the regular-sized energy drink 15 minutes before he passed out."
"That was the biggest issue, how he consumed that energy drink," Watts said.
Davis did not use alcohol or drugs and the autopsy did not reveal any underlying medical conditions that may have played a role in his death, the coroner said.
"This is not an addictive type of situation with him at all,” he added.
Based on his weight, Davis's intake of caffeine exceeded what is considered to be a safe level in that time period of two hours, Watts told BuzzFeed News.