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The viral video apparently showing Troy Ave fending off a mugger won't result in further legal action ... 'cause the cops appear to be confirming the clip is fake.

A rep for the San Diego County Sheriff's Office tells TMZ ... the alleged incident was "not substantiated" -- and, the authorities have closed the case. Play video content

Translation ... the video was all a hoax -- which might not be a crime, but certainly won't do any favors for Troy's image. Getty

ICYMI ... video began circulating online which showed Troy apparently protecting his pal Chef Geoff and fending off a mugger with a gun .

However, sources told us the video was faked for internet clout . No one tried to rob Geoff, and Troy didn't even fire off live

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