The driver of a bus that crashed last month injuring 13 members of the Morehouse College band has died of natural causes.

Ralph Marshall, 63, died Tuesday following a vehicle incident in Southwest Atlanta. The Fulton County Medical Examiner's office reported Wednesday that an autopsy shows no evidence of significant injury from the car wreck incident and the death was instead the result of natural causes. The results of toxicology tests are pending.

Jesse McClardy, the former owner of the bus, told the Atlanta Journal-Constitution that Marshall died of a heart attack.

Marshall was driving one of three buses carrying the "House of Funk" Marching Band to Albany State for a football game on Oct. 31. The bus skidded off Interstate 75 in Henry County and flipped twice.