Footage shows the man – allegedly high on LSD or synthetic drugs – walking around a neighbourhood in Chicago on Monday.
In the video, he can be seen shouting and swearing behind a gated complex with his legs covered in blood.
After officers try to calm him, he charges towards a female cop screaming “get outta here b**ch.”
She then draws her Taser and shouts “get on the ground” before firing.
The cameraman screams: “Oh my God, bro. Shoot his ass. Shoot that mother f**ker. This is a time when you shoot people.”
More Chicago police cars arrive on the scene and the man is taken into custody.
The video was uploaded to Liveleak today with the description: “911 calls on Monday 07/24 evening were made saying a naked man in his 20s appeared to be high on acid when he cut his own penis off.”
A witness said: “This is literally across the street from an elementary school, where kids were present.
“He went to random people’s houses, broke their windows and started hitting and bashing windows of a randomly parked car, naked of course.”
At the end of the footage, the cameraman speculates the man could be on “bath salts".
Daily Star has contacted Chicago Police for comment.