Vincent was with his family Thursday night at the Three Rivers Festival at Headwaters park.
His grandmother, Henrietta Williams, says Vincent was conscious and able to talk to his mother and paramedics as he was taken to a hospital.
Police say the boy may have become frightened and tried to climb off the ride, in which several small vehicles move in a circle.
Festival executive director Shannon White called the accident "very unfortunate." He said festival staff gave Vincent's family members a ride to the hospital.