Half-marathon competitor Jorge Fernandez died soon after collapsing at 9:45 a.m. about 20 yards past the finish line during the Rock 'n' Roll San Antonio Marathon & 1/2 Marathon, the San Antonio Express-News reported.
Fernandez received about 25 minutes of CPR, defibrillator shocks and other attempts to restart his heart before being taken to Christus Santa Rosa Hospital in San Antonio. He was pronounced dead at the hospital at 10:20 a.m.
The Bexar County medical examiner's office had yet to determine a cause of death.
"We are deeply saddened as both the race organizer and as fellow runners, and wish to convey our heartfelt condolences to the participant's family and loved ones," Tracy Sundlun, an official with event coordinator Competitor Group, said in a statement.
Fernandez, who graduated from Texas Tech in 2010, was an avid runner who had completed the half-marathon in San Antonio a year ago. He was a decorated Air Force staff sergeant who had served two tours in Iraq, the last in 2006, and worked as a nurse in the surgical intensive-care unit of University Hospital in San Antonio.