"Stop, stop, he's already dead! - origin

I’m watching the Simpsons episode “Homie the Clown”. In the part where Homer/Krusty is dedicating a new hamburger, he beats the crap out of the “Krustyburglar”.

One kid cries out, “Stop, stop, he’s already dead.”
Where did this originally come from?

Scotty in “ST II: The Wrath of Khan” says, when Kirk rushes to help Spock in Engineering, “He’s dead already.” Could it be a variant of that?

Well, it’s depressing and not a movie quote, but those were Abigail Folger’s last words: “Stop, stop, I’m already dead!”

That is depressing. Was that fairly well known at the time? ie, well known enough for the Simpsons writers to have been parodying it? (poor taste if that is the case, even 20-odd years after the fact)

The Simpsons have used it more than once; in that episode where they had the film festival, it was the last line of Barney’s auteur movie: “Don’t cry for me, I’m already dead. <BURP>”