The article: Actor Cuts Throat on Stage in Knife Mix-Up.
I immediately thought of the Curtains Down level in Hitman: Blood Money, where you can take care of one of your targets by swapping out a prop pistol for a real one. (The target is normally shot in the head with a prop pistol, as part of the opera.)
Fortunately, the actor in the article recovered, and the incident appears to have been the result of incompetence rather than malice.