Letting your dog out for a leak late at night and being startled by what has been dubbed the 'world's most terrifying sound' isn't the ideal way to wrap up your night.
Take a look at how fast this person legged it when they heard the chilling noise in pitch black darkness:
In the clip, you can see a person stood alongside their dog around a pool area, both innocently doing their thing.
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The pet owner has got their phone torch on for the after dark expedition and seems to be simply watching over their pooch as it loiters on the grass.
Everything is calm and still - but suddenly, the pair are disturbed by a blood-curdling sound that scared the living daylights out of them both.
It's hard to put your finger on exactly what it is, although it kind of sounds like a woman screaming at the top of her lungs.
Understandably, both the dog and it's owner ran for their lives and hastily headed back indoors.
Just as they had almost made it inside, the frightening noise rang out again.
Social media users were left unnerved by the spooky footage, captured by a doorbell cam, that was shared in a post on X.
People were desperate to work out what the bizarre sound had been and luckily, some super sleuths came up with a theory about its source.
Apparently, the commotion could have been produced by an Aztec Death Whistle - which is as scary as it sounds.
If your wondering what this ominously named instrument is, keep reading.
Aztec Death Whistle's were first discovered in the arms of a skeleton by archaeologists in 1999 while they were excavating an Aztec temple in Mexico City.
The corpse was clutching two skull-shaped objects in each hand, but the purpose of this remains much debated.
Some think it is a reference to Mictlantecuhtli, the Aztec god of the underworld, while others speculated that they were taken into battle by some warriors.
According to a tech expert James J. Orgill, who shared a YouTube video testing a 3D printed version of the Aztec Death Whistle, excavators who found it initally thought it was just 'some sort of toy'.
"It wasn't until 15 years later for some reason a scientist blew into the hole in the top of it and this is the sound that came out," he told the New York Post.
"The sound that the death whistle makes innately strikes fear into your heart. It was a startling discovery because it sounded like a screaming human."
Since the landmark discovery was made, there has been much speculation about the purpose of an Aztec Death Whistle.
Some believed soldiers used the 'most terrifying sound in the world' to scare off their enemies, but sadly, we're still not 100 percent on what the Aztecs used them for.
Music archaeologist Arnd Adje Both reportedly took CT scans of the original whistles to get a closer look at the inner workings of them before attempting to replicate one.
The subsequent sound it produced was a lot softer than the sharp shriek that was expected, with the expert comparing it to the 'atmospheric noise generated by the wind'.
Both suggested that because of where the Aztec Death Whistle was first found and it's deathly design, it was more likely to have been used in a ceremonial or religious fashion rather than on the battlefield.
Although it sounds eerily similar, the scream that was caught on camera is more likely to have been from an animal. Boo!
Olivia Burke