An actor is playing a character who is in danger. He is screaming at the top of his lungs: "Help me! Help me! I'm in danger!"
Then, for whatever reason, the actor gets in actual danger, like he is in pain and needs actual helps.
How does the actor signal that he is not playing anymore, so that the crew stops filming and comes helping him?
Of course this could be done in many ways, but I'm interested in:
Standard protocols to handle this situation, if there are.