20 people were killed during the filming of 'Rambo'

[snopes]

Comment: I have been hearing that the First Blood (Rambo) series was
discontinued, due to it being the one of the most deadly of a movies.
By deadly I mean it is the movie, which caused the most actor deaths in
the making. I was informed that, there was around 20 acting (movie
involved) people killed in the process of making the movies.(series) I
wouls like to be clarified on this.

And if this is not the most fatal, movie making. Could you tell what
movie was???