Updated 10/10/11 – 6:40 a.m.

CHICAGO (CBS) — A firefighter from Greensboro, N.C., collapsed in the South Loop while running the Chicago Marathon on Sunday and died about two hours later.

William Caviness, 35, was a captain with the Greensboro Fire Department, according to Greensboro Fire Chief Greg Grayson. He was running the marathon with his brother, Sean.

LISTEN: WBBM Newsradio’s Lisa Fielding reports

“Our hearts and prayers go out to the entire Caviness family in this tremendous loss of Captain Will Caviness,” Grayson said in a prepared statement. “The Greensboro Fire Department family is grieving this great loss and will strive to support the Caviness family through this difficult time.”

Caviness’ wife was in Chicago with him for the race. Fellow firefighters said he was a big runner and Greensboro Deputy Fire Chief Clarence Hunter said he was an up and coming leader in the department. He had been a firefighter for eight years

Marathon spokeswoman Robin Monsky said Caviness collapsed near Roosevelt Road and Indiana Avenue. Five emergency doctors working for the marathon attended to him right away and put him in an ambulance.

Doctors who attended to Caviness at the scene got a pulse, but he died an hour and 45 minutes later at the hospital.

Caviness was pronounced dead at 12:03 p.m. at Mercy Hospital and Medical Center, according to the Cook County Medical Examiner’s office. A cause of death had yet to be determined, but authorities suspected Caviness died of cardiac arrest.

An autopsy is planned for Monday, according to the medical examiner’s office.

Caviness was running to raise money for a charity that helps burn victims.

The last death at the marathon was in 2007, when the marathon was halted after a runner died and at least 49 others were hospitalized due to heat-related illnesses amid record-setting heat and humidity.

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