Ian A. Hudson, a New Mexico-based principal cast member who plays an outlaw in the film, tells TMZ ... the show can't go on because slain cinematographer Halyna Hutchins was the vision behind the movie.

While Ian says it's ultimately up to director Joel Souza and the rest of the creative minds, he thinks the movie just wouldn't be the same without Halyna and Joel working in tandem ... and it's time to throw in the towel.

Remember ... Ian was smack in the center of some of the gun scenes in the movie, and he told us his shootout scene felt "life-threatening" because real firearms were firing blanks at him, resulting in him being struck by small bits of cardboard and a rush of air.

As you know ... Alec pulled the trigger on a gun that fired the fatal live round of ammo that killed Halyna and injured Joel.

Assistant director Dave Halls gave Alec the gun used in the scene, telling him it was a "cold gun" ... meaning it was not loaded.

There's an ongoing investigation into the incident and authorities say criminal charges are still on the table for all involved ... which could make it even harder for the movie to continue.

We covered it all on the latest episode of The TMZ Podcast.