A car barreled through a throng of speedboat racing fans gathered for a boat race, injuring 11 people and plunging 25 feet out into the Ohio River.
Police said four of the people were injured seriously in the accident Sunday afternoon at the Madison Regatta. There were no fatalities.
"I saw one young lady just frozen in her path, just standing at the water's edge and the car ran directly over the top of her," said David Edds, of Owensboro, Kentucky. "It was the most horrifying thing that I have ever seen."
The driver, Michael Bowen, 18, was taken to a hospital in Louisville, Kentucky, about 40 miles away, officials said. Police said Bowen was slumped over the steering wheel as the vehicle approached a crowd barrier along the riverfront. He was unconscious when he was pulled from the water, Madison Police Chief Bob Wolf said.
A juvenile passenger in the car also was hospitalized.
Police did not know what caused the accident, but said charges could be filed.
Police said the car drove through the crowd, hit a golf cart used by officials who ducked for cover and then went airborne.
Madison is in southeast Indiana, midway between Louisville and Cincinnati. The annual race for unlimited hydroplanes draws thousands of people to the riverside community of about 13,000 every Fourth of July weekend.