Here's a report I found dating back from 1983. It's from an "E. Murphy."

This is truly a scary story and just gives me the guni gugus.

Direct quotes from E. Murphy while talking to a person named Gus:

"Look at the motherfarkers, you know
how I found out they was bigfoot? When I took your kids fishing last week. I put the motherfarkers in the boat Gus. And I took the worm and I put it on the hooks. And they both sat there, and put the poles down in the boat. And slammed their face in the water, for 5 mins.

And I think what the fark are these kids doing? Then they start movin their heads like this and the motherfarkers come up with fish.

I jumped back and said can you believe this
motherfarkin [Bleeeeep!]????

Then the kid took the fish out of his mouth,
looked at his brother and said: "Guni gugu!"

I said, what the fark is going on here?

Normal kids don't do [Bleeeeep!] like that, Gus! But I'll tell you somethin' motherfarker! You can take your motherfarker hairy fat arse white mustache biatch out the fark. You can go upstairs and get the motherfarkin' dog and scoop up the [Bleeeeep!]...and take Eddie and get these motherfarker long Angela Davis afro-ware motherfarker kids of yours......and put them in the motherfarker guni gugu-mobile and get the fark out!

And if my wife don't like it she can get the fark out too!"