This is from the original 1956 Invasion of the Body Snatchers.  This is how director Don Siegel wanted the film to end, with Kevin McCarthy vainly warning drivers that they’re coming for them.  The studio, however, insisted that Siegel add a scene that suggested that the authorities might be able to stop the invasion.

Incidentally, Don Siegel was born 108 years ago, today!  He was one of the great American genre directors.  Unfortunately, he didn’t really do enough horror films for me to devote a 4 Shots from 4 Films post to him but, that being said, it’s impossible to keep track of how many subsequent horror films would be influenced by Invasion of the Body Snatchers.