A ride car came loose, throwing out a 16 year old passenger, and leaving the other hanging precariously. The boy remaining in the car was injured by safety barriers as the ride continued to turn. He was treated in intensive care for extensive injuries including a collapsed lung. The boy who was thrown from the ride suffered injuries including a broken nose. Source
Accidents
Theme parks and roller coasters are statistically very, very, very safe. Out of the millions of people who ride the thousands of rides every year, there are only a small handful of incidents. You are statistically more likely to be involved in an accident driving to an amusement park than having one at a park. The rarity of accidents is one reason why the media report them, similar to plane crashes.
Every important element of a ride is inspected on a regular basis and every ride is tested every day without passengers before it opens. A ride might not open, or a safety system might activate, if there is an imperfection. For theme parks to operate, they must obtain insurance and one stipulation is their rides are frequently inspected and signed off by a strict Health & Safety governing body. Every theme park does what they can to prevent accidents because the negative press would be bad for business.
Having said all that, theme park accidents still happen…
Trafikplasten, Furuviksparken, Gävleborg, Sweden
A 31-year-old man was hospitalized with blood poisoning and internal injuries after he boarded the kiddie car ride in an attempt to assist his daughter and his rectum became impaled on a tow hitch that protruded from behind the vehicle. Source (in Swedish)

Kingda Ka, Six Flags Great Adventure, New Jersey, USA
A man suffered neck and face injuries when a bird flew into his face while on the coaster. Source
Vampire, Six Flags La Ronde, Québec, Canada
A maintenance worker was struck by the coaster’s moving train and killed instantly after he entered a restricted area. Source
Ladybird Coaster, Lightwater Valley, North Yorkshire, UK
A 5-year-old girl suffered ankle damage after she stuck her foot outside of the train. The ride has since been modified with higher sides to the trains. Source
Tomb Blaster, Chessington World of Adventures, London, UK
A 4-year-old girl was seriously injured when she when she fell 14 feet (4m) from the raised, fenced queue line section. Source
Pollydrop, Adventure Wonderland, Dorset, UK
The main cable on the drop tower ride snapped while the ride car was 3/4 of the way up. The back-up cable activated, meaning the three riders escaped with only minor injuries. Source
Commander, Bremer Osterwiese, Bremen, Germany
Two passengers were injured when an gondola ripped from its swing arm. A similar accident happened in May 2010, injuring nine on-lookers. This time a cable prevented the gondola from leaving the ride platform. Source (in German)
La Tour Eiffel, Hopi Hari, São Paulo, Brazil
A 14-year-old girl fell 98 feet (30m) to her death when her restraint opened at the moment the brakes were applied. The seat should have been marked “out of order”. Source
Drop Tower, Van Huong Mai Amusement Park, Chau Phu, Vietnam
Five people were injured when the drop tower ride suffered a “technical fault” and fell to the ground. Source
