I'd also heard this part was a detail that was unchanged from the true story.
When it was revealed that when the young couple thought they were attempting to talk to "foreign workers" that they were actually talking to cattle.
Somehow that scene was a microcosm of the effect that the drugs had. Chilling and effective, IMO.
As the real couple died, I don't see that anyone can know what they really saw.
But it does seem safe to assume that they didn't encounter groups of Mexicans and African-Americans in costume.
Well, I thought that Nancy would have been able to hear the cattle lowing during that call; it's possible the real dispatcher did. And I agree that the scene was chilling - pardon the pun. I just thought it was very strange that the two would experience identical hallucinations.
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