Harrowing footage captured a man screaming and writhing around on the ground after allegedly taking the 'zombie drug' Black Mamba.
Rapper Jess1 said the man appeared "possessed" and to be suffering hallucinations as he lay on the floor with his 'eyes rolling to the back of his head' and his trousers pulled down.
He said the man's pals were supposedly laughing before the 25-year-old rapper decided to voice his concerns during the incident on August 2 in Derby city centre.
Jess1, from Derby, said: "The effect of it is really scary. He looked like he was dying.
"They look like they're fighting something as if they are being possessed.