Crash in this video, along with the Tour de Corse accident in which driver Henri Toivonen and Sergio Cresto died in a fireball led to the complete ban of the Group B class in rally racing. This was in 1986.
At the Rally Portugal, part of the World Rally Championship, 3 spectators were killed and more than 30 injured after a racing car plowed through the crowd standing outside of a corner. I’m actually rather surprised that there were only 3 casualties. Please note, the video says that 4 people died but according to my research, only 3 did.
And thus, thanks to the spectators wanting to get too close to the action for a little adrenaline rush, the short-lived Group B era, notable for featuring some of the fastest and most powerful rally cars ever built has come to an end after just 4 years of running.
Also check out the BBC documentary on The Killer Years of Grand Prix.