Mindbender, 1986
On June 14, 1986, the wheel assembly of the fourth car of the Mindbender roller coaster ride at Galaxyland Amusement Park in Alberta, Canada came off the track. This caused the car to swerve from side to side. Then the lap bar restraints accidentally unlocked causing four passengers to fall on the hard floor. But the nightmare didn’t end there. The train tried to complete the final loop but couldn’t. Instead, it rolled back and crashed into a pillar. Three of the passengers died and the surviving rider suffered permanent injuries.