William Caviness was pronounced dead at 12:03 p.m. at Mercy Hospital and Medical Center, according to the Cook County Medical Examiner’s office.
An apparent cause of death was not immediately known.
"Our hearts and prayers go out to the entire Caviness family in this tremendous loss of Capt. Will Caviness," said Greensboro Fire Department Chief Greg Grayson. "The Greensboro Fire Dept. family is grieving this great loss and will strive to support the Caviness family through this difficult time."
Caviness collapsed at 10:39 a.m. at 1200 S. Indiana, police said. According to the marathon route map, that's near the 26-mile marker, a short distance from the finish line.
"He was a fine man," Grayson said.
Caviness was running for the IAFF Burn Foundation, according to his Facebook page.
"Less than 24 hours," reads the final message. "I truly appreciate all the support that you all have shown for my run with the Burn Foundation. WE have raised well over $2000. You all are AWESOME. Thanks again. Will."
Race officials said the race was safer overall this year. Organizers said there were 54 hospital transports compared with 100 in 2010 and 85 in 2008.