One of the actors immediately let go of his fake assault rifle. But another held onto his replica handgun, forcing officers to make a life-or-death choice. An officer knocked the gun from the actor's hand and handcuffed him, drawing a peaceful climax to what could have been something far worse.
Police said it showed the dangers of movie-making for amateur film crews that don't get permits and follow proper steps before taking to the streets.
Attempts to reach the film's director were unsuccessful. The students declined to tell police what college they were from.
The officers responded to the shop after receiving a 911 call from a woman who reported seeing an armed, masked gunman inside Classic Coffee in Glendora, a suburb east of Los Angeles that rarely sees Hollywood film crews.
Police said there was nothing to indicate a short movie was being shot.
The students were allowed to keep the fake weapons and weren't facing charges. They were given a lecture by officers about the dangers they created and went on their way.