To ensure a reaction of surprise and spontaneous terror, director John McTiernan trapped Alan Rickman (also known as Hans Gruber) during the filming of the famous Crystal Piège scene where he falls into the void at the end of the film. .
Because the scene was complicated to film and would be difficult to do multiple takes, McTiernan decided to throw Alan Rickman into the void at a time when he wasn’t expecting it.
The actor was suspended above the void (in the studio), and had to be released when the director shouted 1… 2… 3…!
Except McTiernam had warned his team to drop Rickman when he said “2”!
The trick worked, as Rickman was genuinely surprised and believed there was a problem.
It is therefore an expression of spontaneous surprise that we see on his face in the film, as it is this famous shot that was used.