A maintenance worker in his late 50’s was critically injured when he fell 30-50 feet (9-15 m) to the ground while working on the Gravity Group twister coaster. 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…
Old Port Ferris Wheel, Montreal, Quebec, Canada
A 22-year-old employee died on Christmas day when he was tasked to clear snow from the La Grande Roue De Montréal attraction while it was in operation. As he walked onto a raised platform near the drive wheels his coat got caught in one of them, dragging him in and crushing him between two parts of the machine. Source
3D Maze, Tojoko Omocha Okoku, Kato, Japan
Six people, including a six-year-old girl, were injured after falling from the third-story section of the 3D labyrinth attraction at Lake Tojo Toy Kingdom. Both a 27-year-old woman and a 24-year-old man fractured a hip bone. The man fell while holding his one-year-old daughter, who sustained no injuries. Source
Fun House, Gilberdyke Funfair, Hull, UK
A six-year-old girl had her finger severed above the knuckle when she got it stuck after falling on a rotating walkway. Source
Haunted Mine Drop, Glenwood Caverns Adventure Park
A 6-year-old girl fell 110 feet (33.5 m) to her death on the Soaring Eagle underground drop ride. It was later determined that her seat belt was fastened under, rather than over her lap. Source
Superflip 360, Funland, Rehoboth Beach, Delaware, USA
Two girls, 14 and 15 years old, and one 16-year-old boy were injured by flying metal when a compressed air-tank near the Chinese manufactured inverting pendulum ride exploded. All three were taken to hospital, the male with a serious head injury. Source
Kamikaze, Hayrola Luna Park, Istanbul, Turkey
A 19-year-old teenager died while riding on the pendulum style attraction when she fell unconscious and choked on her own vomit. Source
Top Thrill Dragster, Cedar Point, Sandusky, Ohio, USA
A 44-year-old woman suffered severe brain injuries when a metal object that flew off the Intamin strata coaster struck her head as she was waiting in line for the ride. The coaster closed and will be modified as a new Zamperla Lightning coaster. Source
Sky Ride, Lagoon, Farmington, Utah, USA
A 32-year-old man died after falling 50 feet (15 m) to the ground from the park’s Hopkins Sky Ride. The man was seen dangling from outside the chair with both hands holding on the safety bar before he fell. Source
Runaway Timber Train, Landmark Forest Adventure Park, Scotland
Eight people, including two children, suffered minor injuries when the I.E. Park junior coaster partially derailed. Source