Paul Duncan, who had a brief stint in the NFL with the Denver Broncos, died on July 16 at the age of 35.
His wife, Ellen Duncan, confirmed his death in an Instagram post later that day.
"Yesterday, Friday July 15th, Paul went into cardiac arrest while on a run in our neighborhood," she wrote. "Today he was pronounced brain dead."
His body will be donated to people in need of organs and to medical research.
The medical examiner's office in DeKalb County, Georgia confirmed his death.
Paul leaves behind his two daughters, Dillon, 6, and Sloane, 4.
Before Paul joined the NFL, he was an offensive lineman for the Notre Dame Fighting Irish football team from 2005 to 2009.
The Notre Dame football team mourned his death in a tweet: "Our prayers go out to the family and friends of Paul Duncan. A great teammate, but more importantly a loving husband and father."