SAN ANTONIO – Half-marathon runner Jorge Fernandez died of probable heat stroke, the Bexar County Medical Examiner's Office said.
Autopsy results were released Tuesday.
Fernandez, 32, died after finishing last year's Rock n' Roll San Antonio Marathon.
Temperatures that Sunday reached up to 79 degrees during the marathon and race officials said dozens of runners had to be treated for heat related injuries, some were even taken away in ambulances.
While Fernandez was running, temperatures were below 70, but with a high dew point and 100 percent humidity.
He finished the race about 9:45 a.m.
Neighbors of Fernandez said the veteran was in great shape.
Sally Rios with San Antonio Road Runners said without knowing how Fernandez was feeling during the race, the best advice is to listen to your body.
"You've been training for a marathon and if you train in San Antonio, you know how hot it gets," said Rios. "You know you have to take water, you know that's a must."
"You could have too many volunteers but if a runner is not stopping to take water, there's nothing you can do," she added.
A tribute to Fernandez is planned for next year's race.