Soulja Boy Threatens to Kill Ex-GF's New Guy

8/19/2016 12:08 PM PDT
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12:57 PM PT -- Nia tells TMZ she's NOT calling cops to report Soulja. She says she doesn't have a BF, and the person he threatened is just an Internet troll trying to piss off the rapper.

A rep for Soulja claims the gun was a fake, and adds he's already reached out to Nia to apologize. 

Soulja Boy is making disturbing threats against the guy he thinks took his place ... with his ex-girlfriend.

The "Crank That" rapper made the vicious threat Friday in a video post ... waving and pointing what appears to be a Glock with an extended magazine.

It's unclear why the threat's being directed at Nia Riley and her BF. Not the smartest move -- especially considering Soulja's on probation for a weapons charge

We've reached out to Soulja, so far no word back.