MIAMI, Florida (CNN) -- A boy who died this summer after riding the "Mission Space" ride at Walt Disney World's Epcot Center in Orlando had a pre-existing heart condition, according to autopsy reports.Four-year-old Daudi Bamuwamye lost consciousness while on the ride in June. The autopsy report released Tuesday by the Orange County Medical Examiner's Office states the boy died as a result of the heart condition.Toward the end of the ride the boy became rigid, and when the ride ended, Bamuwamye's body "was limp and unresponsive," his mother, Agnes Bamuwamye, told authorities. Paramedics and a park employee tried to revive him. He died later at the hospital.The autopsy report states the boy suffered from a heart condition that affected his heart's left ventricle. The boy's family was unaware of the condition, said a spokesman in the medical examiner's office."Mission Space" opened in 2003, and seven people who have ridden it have been taken to the hospital for chest pains, fainting or nausea. Signs posted near the attraction, which simulates a rocket blastoff and mission to Mars, warns that riders should be in good health.Disney's Web site advises that riders "should be free from high blood pressure, heart, back or neck problems, motion sickness, or other conditions that could be aggravated by this adventure. Expectant mothers should not ride."A statement from Walt Disney World extended sympathies to the family and declined to comment further on the boy's death.