TUCSON, Ariz. (AP) -- Authorities in Tucson say a medical condition may have precipitated a collision in which a 59-year-old bicyclist was killed during a weekend race John Henderson of Tucson was killed Saturday on an Interstate 10 frontage road in northwest Tucson when struck by a vehicle driven by 78-year-old Steven Lang of Marana. The state Department of Public Safety says the possibility of a medical condition experienced by Lang is being investigated as contributing to the collision. It occurred as Henderson was riding in a lane designated for the El Tour de Tucson race. Northwest Fire District Capt. Adam Goldberg says a medical condition could explain why Lang lost control of his vehicle.