A Missouri community was left devastated when a teenage runner died suddenly after crossing the finish line at a half marathon Saturday.

Rudy Zevallos Jr.,Surpassing 18, died after finishing the 13.1-mile race in Waynesville, about 133 miles southwest of St. Louis, according to organizers from the Frog Hill Half Marathon, 10K and Leapfrog 5K.

“The exact cause of his death is unclear at this time, but we do know his body temperature reached a fatal level and his heart stopped,” organizers shared on Facebook Monday.

The Pulaski County Coroner's Office won't have Rudy Zevallos Jr.'s cause of death for 6 to 8 weeks, the office told USA TODAY Thursday morning.

Zevallos had just celebrated his 18th birthday in August and he was a senior at Lebanon High School. He planned to graduate early in December and join the Marine Corps like his father, Rudy Zevallos Sr., organizers said. 

The Lebanon R-3 School District also shared thoughts on Zevallos’ passing over the weekend, offering condolences to his family and friends.

“Let us stand together and support one another as we face this difficult loss,” the district shared.

Fallen teenager was loved by many

Zevallos was “a remarkable friend, student, brother, and son,” organizers of the Frog Hill event shared on the event’s Facebook page. 

He was competitive and determined and was an avid student of the Bible. He often read books about investing, self-improvement and worked hard to be the best version of himself he could be, they said.

When he wasn’t at school, he hiked with his girlfriend, Olivia and worked at 7Brew drive-thru coffee shop. He also spent time working on his car, playing poker and having game nights with his family. 

His biggest passion, organizers said, was fitness. He trained in jiu-jitsu and played soccer as a child. He also played football, wrestled and ran track throughout middle and high school. 

“Rest was a foreign concept to him,” organizers wrote, lovingly calling him Junior. 

His goal on Saturday, organizers said, was to complete the half marathon in under two hours. He completed it in an hour and 58 minutes.

The Zevallos family started a GoFundMe to raise money for his memorial service and as of Thursday, they’ve raised over $27,000.

“We are overwhelmed with the support and love from every single one of you,” the family shared in an update. “We thank you from the bottom of our hearts. Jr’s service is going to be amazing.”

He is survived by his mother, his father, two older sisters and a future brother-in-law. 

Saleen Martin is a reporter on USA TODAY's NOW team. She is from Norfolk, Virginia – the 757. Follow her on Twitter at@SaleenMartin or email her at[email protected].